diff --git a/Cargo.lock b/Cargo.lock
index d394025..558d63d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8,12 +8,6 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "aae1277d39aeec15cb388266ecc24b11c80469deae6067e17a1a7aa9e5c1f234"
 
-[[package]]
-name = "anyhow"
-version = "1.0.75"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a4668cab20f66d8d020e1fbc0ebe47217433c1b6c8f2040faf858554e394ace6"
-
 [[package]]
 name = "byteorder"
 version = "1.4.3"
@@ -54,7 +48,6 @@ checksum = "5443807d6dff69373d433ab9ef5378ad8df50ca6298caf15de6e52e24aaf54d5"
 name = "fot-save-edit"
 version = "0.1.0"
 dependencies = [
- "anyhow",
  "byteorder",
  "deflate",
  "encoding_rs",
diff --git a/Cargo.toml b/Cargo.toml
index 27dfe13..c6bb7ae 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,7 +6,6 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-anyhow = "1.0.75"
 byteorder = "1.4.3"
 deflate = "1.0.0"
 encoding_rs = "0.8.33"
diff --git a/src/fot.rs b/src/fot.rs
index 36cfddb..f917159 100644
--- a/src/fot.rs
+++ b/src/fot.rs
@@ -3,6 +3,7 @@ mod decoder;
 mod entity;
 mod entitylist;
 mod esh;
+mod ferror;
 mod fstring;
 mod raw;
 pub mod save;
diff --git a/src/fot/attributes.rs b/src/fot/attributes.rs
index 530881a..4fab980 100644
--- a/src/fot/attributes.rs
+++ b/src/fot/attributes.rs
@@ -1,9 +1,9 @@
 use crate::fot::decoder::Decoder;
 
 use super::esh::{ESHValue, ESH};
+use super::ferror::FError as FE;
 use super::stream::{ReadStream, WriteStream};
 use super::tag::Tag;
-use anyhow::{anyhow, Result};
 use indexmap::IndexMap;
 
 const MAX_STATS: usize = 7;
@@ -273,13 +273,13 @@ pub struct Attributes {
 }
 
 impl Attributes {
-    pub fn from_binary(bin: &[u8]) -> Result<Self> {
+    pub fn from_binary(bin: &[u8]) -> Result<Self, FE> {
         let mut rd = ReadStream::new(bin, 0);
 
         let size1 = rd.read_u32()?;
         let esh: ESH = rd.read()?;
         if esh.props["Binary"] == ESHValue::Bool(false) {
-            return Err(anyhow!("Attributes Binary == false"));
+            return Err(FE::AttributesNonBinary);
         }
 
         let mut stats: IndexMap<&'static str, u32> = IndexMap::with_capacity(7);
@@ -339,11 +339,11 @@ impl Attributes {
                 addictions,
             })
         } else {
-            return Err(anyhow!("Attributes has no esbin"));
+            return Err(FE::AttributesNoESBIN);
         }
     }
 
-    pub fn into_binary(mut self) -> Result<Vec<u8>> {
+    pub fn into_binary(mut self) -> Result<Vec<u8>, FE> {
         let esbin = {
             let mut wd = WriteStream::new(self.enc_size);
 
diff --git a/src/fot/decoder.rs b/src/fot/decoder.rs
index 8ed4058..69a087b 100644
--- a/src/fot/decoder.rs
+++ b/src/fot/decoder.rs
@@ -1,32 +1,32 @@
+use super::ferror::FError as FE;
 use super::stream::{ReadStream, WriteStream};
-use anyhow::{anyhow, Result};
 use std::str;
 
 pub trait Decoder: Sized {
-    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self>;
-    fn encode(&self, wd: &mut WriteStream) -> Result<()>;
+    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self, FE>;
+    fn encode(&self, wd: &mut WriteStream) -> Result<(), FE>;
     fn get_enc_size(&self) -> usize;
 }
 
 pub trait DecoderCtx<DCtx, ECtx>: Sized {
-    fn decode<'a>(rd: &mut ReadStream<'a>, ctx: DCtx) -> Result<Self>;
-    fn encode(&self, wd: &mut WriteStream, ctx: ECtx) -> Result<()>;
+    fn decode<'a>(rd: &mut ReadStream<'a>, ctx: DCtx) -> Result<Self, FE>;
+    fn encode(&self, wd: &mut WriteStream, ctx: ECtx) -> Result<(), FE>;
     fn get_enc_size(&self) -> usize;
 }
 
 impl Decoder for String {
-    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self> {
+    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self, FE> {
         let bytes = rd.as_byte_arr();
         let pos = match bytes.iter().position(|&c| c == 0) {
             Some(pos) => pos,
-            None => return Err(anyhow!("No zero-terminator found")),
+            None => return Err(FE::NoZeroTerminator),
         };
         let str = str::from_utf8(rd.as_bytes(pos)?)?;
         rd.skip(1);
         Ok(str.to_string())
     }
 
-    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
+    fn encode(&self, wd: &mut WriteStream) -> Result<(), FE> {
         wd.write_bytes(self.as_bytes());
         wd.write_u8(0)?;
         Ok(())
diff --git a/src/fot/entity.rs b/src/fot/entity.rs
index c02d7d3..0884a3c 100644
--- a/src/fot/entity.rs
+++ b/src/fot/entity.rs
@@ -2,8 +2,8 @@ use super::attributes::Attributes;
 use super::decoder::DecoderCtx;
 use super::entitylist::{EntityEncoding, EntityList};
 use super::esh::{ESHValue, ESH};
+use super::ferror::FError as FE;
 use super::stream::{ReadStream, WriteStream};
-use anyhow::{anyhow, Result};
 
 pub const NO_FLAGS: u32 = 0;
 pub const NO_ESH: usize = 0xFFFF;
@@ -16,34 +16,34 @@ pub struct Entity {
 }
 
 impl Entity {
-    pub fn get_esh(&self) -> Result<&ESH> {
+    pub fn get_esh(&self) -> Result<&ESH, FE> {
         match &self.esh {
             Some(esh) => Ok(esh),
-            None => Err(anyhow!("Entity has no ESH")),
+            None => Err(FE::EntityNoESH),
         }
     }
 
-    pub fn get_esh_mut(&mut self) -> Result<&mut ESH> {
+    pub fn get_esh_mut(&mut self) -> Result<&mut ESH, FE> {
         match &mut self.esh {
             Some(esh) => Ok(esh),
-            None => Err(anyhow!("Entity has no ESH")),
+            None => Err(FE::EntityNoESH),
         }
     }
 
-    pub fn get_attributes(&self) -> Result<Attributes> {
+    pub fn get_attributes(&self) -> Result<Attributes, FE> {
         let value = match self.get_esh()?.get("Attributes") {
             Some(value) => value,
-            None => return Err(anyhow!("Entity has no Attributes")),
+            None => return Err(FE::EntityNoAttributes),
         };
 
         if let ESHValue::Binary(bin) = value {
             Ok(Attributes::from_binary(&bin)?)
         } else {
-            Err(anyhow!("Attributes is not binary"))
+            Err(FE::AttributesNonBinary)
         }
     }
 
-    pub fn set_attributes(&mut self, attrs: Attributes) -> Result<()> {
+    pub fn set_attributes(&mut self, attrs: Attributes) -> Result<(), FE> {
         self.get_esh_mut()?
             .set("Attributes", ESHValue::Binary(attrs.into_binary()?));
 
@@ -52,7 +52,7 @@ impl Entity {
 }
 
 impl DecoderCtx<&mut EntityList, &EntityList> for Entity {
-    fn decode<'a>(rd: &mut ReadStream<'a>, ctx: &mut EntityList) -> Result<Self> {
+    fn decode<'a>(rd: &mut ReadStream<'a>, ctx: &mut EntityList) -> Result<Self, FE> {
         let offset = rd.offset();
         Ok(match ctx.get_entity_encoding() {
             EntityEncoding::File => {
@@ -87,7 +87,7 @@ impl DecoderCtx<&mut EntityList, &EntityList> for Entity {
         })
     }
 
-    fn encode(&self, wd: &mut WriteStream, ctx: &EntityList) -> Result<()> {
+    fn encode(&self, wd: &mut WriteStream, ctx: &EntityList) -> Result<(), FE> {
         match ctx.get_entity_encoding() {
             EntityEncoding::File => {
                 wd.write(ctx.get_type_name(self.type_idx))?;
diff --git a/src/fot/entitylist.rs b/src/fot/entitylist.rs
index 498cf7c..b177fba 100644
--- a/src/fot/entitylist.rs
+++ b/src/fot/entitylist.rs
@@ -1,10 +1,9 @@
 use super::decoder::{Decoder, DecoderCtx};
 use super::entity::Entity;
+use super::ferror::FError as FE;
 use super::fstring::{FString, FStringEncoding};
 use super::stream::{ReadStream, WriteStream};
 use super::tag::{CTag, Tag};
-use anyhow::anyhow;
-use anyhow::Result;
 use std::path::Path;
 
 #[derive(Clone, Copy, PartialEq)]
@@ -66,10 +65,10 @@ impl EntityList {
         &mut self.ents[id - 1]
     }
 
-    pub fn dump_to_entfile(&self, ent: &Entity, path: &Path) -> Result<()> {
+    pub fn dump_to_entfile(&self, ent: &Entity, path: &Path) -> Result<(), FE> {
         let esh = match &ent.esh {
             Some(esh) => esh,
-            None => return Err(anyhow!("entity has no esh")),
+            None => return Err(FE::EntityNoESH),
         };
 
         let tag = DEFAULT_ENTITY_TAG.to_tag();
@@ -87,7 +86,7 @@ impl EntityList {
 }
 
 impl DecoderCtx<EntityEncoding, EntityEncoding> for EntityList {
-    fn decode<'a>(rd: &mut ReadStream<'a>, ctx: EntityEncoding) -> Result<Self> {
+    fn decode<'a>(rd: &mut ReadStream<'a>, ctx: EntityEncoding) -> Result<Self, FE> {
         let offset = rd.offset();
         let mut ent_list = EntityList {
             encoding: ctx,
@@ -137,7 +136,7 @@ impl DecoderCtx<EntityEncoding, EntityEncoding> for EntityList {
         })
     }
 
-    fn encode(&self, wd: &mut WriteStream, ctx: EntityEncoding) -> Result<()> {
+    fn encode(&self, wd: &mut WriteStream, ctx: EntityEncoding) -> Result<(), FE> {
         match ctx {
             EntityEncoding::File => {
                 for ent in self.ents.iter() {
diff --git a/src/fot/esh.rs b/src/fot/esh.rs
index 6f5bf86..1317139 100644
--- a/src/fot/esh.rs
+++ b/src/fot/esh.rs
@@ -1,8 +1,8 @@
 use super::decoder::Decoder;
+use super::ferror::FError as FE;
 use super::fstring::FString;
 use super::stream::{ReadStream, WriteStream};
 use super::tag::Tag;
-use anyhow::Result;
 use indexmap::IndexMap;
 use std::fmt;
 
@@ -77,7 +77,7 @@ impl ESHValue {
 }
 
 impl Decoder for ESHValue {
-    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self> {
+    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self, FE> {
         let data_type = rd.read_u32()?;
         let data_size = rd.read_u32()?;
 
@@ -120,7 +120,7 @@ impl Decoder for ESHValue {
         })
     }
 
-    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
+    fn encode(&self, wd: &mut WriteStream) -> Result<(), FE> {
         match self {
             ESHValue::Unknown(unk) => {
                 wd.write_u32(unk.data_type)?;
@@ -266,7 +266,7 @@ impl ESH {
 }
 
 impl Decoder for ESH {
-    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self> {
+    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self, FE> {
         let offset = rd.offset();
         let tag: Tag = rd.read()?;
 
@@ -286,7 +286,7 @@ impl Decoder for ESH {
         })
     }
 
-    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
+    fn encode(&self, wd: &mut WriteStream) -> Result<(), FE> {
         wd.write(&self.tag)?;
 
         wd.write_u32(self.props.len() as u32)?;
diff --git a/src/fot/ferror.rs b/src/fot/ferror.rs
new file mode 100644
index 0000000..5053703
--- /dev/null
+++ b/src/fot/ferror.rs
@@ -0,0 +1,51 @@
+#[derive(Debug)]
+pub enum FError {
+    IOError(std::io::Error),
+    Utf8Error(std::str::Utf8Error),
+    DeflateError(String),
+    NoWorld,
+    NoCampaign,
+    UnknownWorldSize,
+    StreamOverflow(usize, usize, usize),
+    NoZeroTerminator,
+    EntityNoESH,
+    EntityNoAttributes,
+    AttributesNonBinary,
+    AttributesNoESBIN,
+}
+
+impl std::fmt::Display for FError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        use FError as FE;
+        match self {
+            FE::IOError(e) => write!(f, "IOError {}", e),
+            FE::Utf8Error(e) => write!(f, "Utf8Error {}", e),
+            FE::DeflateError(e) => write!(f, "DeflateError {}", e),
+            FE::NoWorld => write!(f, "No world found in file"),
+            FE::NoCampaign => write!(f, "No campaign found after world"),
+            FE::UnknownWorldSize => write!(f, "Unable to determine world block size"),
+            FE::StreamOverflow(offset, size, read) => write!(
+                f,
+                "stream read {} at offset {} overflow size {}",
+                read, offset, size
+            ),
+            FE::NoZeroTerminator => write!(f, "No zero-terminator when String::decode"),
+            FE::EntityNoESH => write!(f, "Entity has no ESH"),
+            FE::EntityNoAttributes => write!(f, "Entity has no Attributes"),
+            FE::AttributesNonBinary => write!(f, "Attributes Binary != true"),
+            FE::AttributesNoESBIN => write!(f, "Attributes has no esbin"),
+        }
+    }
+}
+
+impl From<std::io::Error> for FError {
+    fn from(value: std::io::Error) -> Self {
+        FError::IOError(value)
+    }
+}
+
+impl From<std::str::Utf8Error> for FError {
+    fn from(value: std::str::Utf8Error) -> Self {
+        FError::Utf8Error(value)
+    }
+}
diff --git a/src/fot/fstring.rs b/src/fot/fstring.rs
index 415b7b4..fa39ce7 100644
--- a/src/fot/fstring.rs
+++ b/src/fot/fstring.rs
@@ -1,6 +1,6 @@
 use super::decoder::Decoder;
+use super::ferror::FError as FE;
 use super::stream::{ReadStream, WriteStream};
-use anyhow::Result;
 use encoding_rs::WINDOWS_1251;
 use std::borrow::Borrow;
 use std::fmt;
@@ -22,7 +22,7 @@ pub struct FString {
 }
 
 impl Decoder for FString {
-    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self> {
+    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self, FE> {
         //let mut rdr = Cursor::new(&raw.mem[offset..]);
         let flen = rd.read_u32()? as usize;
         let len = flen & !(1 << 31);
@@ -48,7 +48,7 @@ impl Decoder for FString {
         }
     }
 
-    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
+    fn encode(&self, wd: &mut WriteStream) -> Result<(), FE> {
         let (chars, _, _) = WINDOWS_1251.encode(self.str.as_str());
         if self.encoding == FStringEncoding::ANSI {
             wd.write_u32(chars.len() as u32 & !(1 << 31))?;
diff --git a/src/fot/raw.rs b/src/fot/raw.rs
index 425adb4..3315b26 100644
--- a/src/fot/raw.rs
+++ b/src/fot/raw.rs
@@ -1,4 +1,4 @@
-use anyhow::Result;
+use super::ferror::FError as FE;
 use memmem::{Searcher, TwoWaySearcher};
 use std::fs;
 use std::fs::OpenOptions;
@@ -31,7 +31,7 @@ impl Raw {
         None
     }
 
-    pub fn load_file(path: &Path) -> Result<Raw> {
+    pub fn load_file(path: &Path) -> Result<Raw, FE> {
         let mem = fs::read(path)?;
 
         Ok(Self {
@@ -41,7 +41,7 @@ impl Raw {
         })
     }
 
-    pub fn assemble_file(&self, path: &Path, blocks: Vec<Raw>) -> Result<()> {
+    pub fn assemble_file(&self, path: &Path, blocks: Vec<Raw>) -> Result<(), FE> {
         let mut file = BufWriter::new(
             OpenOptions::new()
                 .create(true)
@@ -76,7 +76,7 @@ impl Raw {
         Ok(())
     }
 
-    pub fn dump(&self, path: &Path) -> Result<()> {
+    pub fn dump(&self, path: &Path) -> Result<(), FE> {
         let mut file = BufWriter::new(
             OpenOptions::new()
                 .create(true)
diff --git a/src/fot/save.rs b/src/fot/save.rs
index d047a77..a4bac2b 100644
--- a/src/fot/save.rs
+++ b/src/fot/save.rs
@@ -1,9 +1,8 @@
 use super::decoder::DecoderCtx;
+use super::ferror::FError as FE;
 use super::raw::Raw;
 use super::stream::{ReadStream, WriteStream};
 use super::world::World;
-use anyhow::anyhow;
-use anyhow::Result;
 use byteorder::{ByteOrder, LittleEndian};
 use std::path::Path;
 use std::str;
@@ -17,18 +16,18 @@ impl Save {
     const WORLD_TAG: &str = "<world>";
     const CAMPAIGN_TAG: &str = "<campaign>";
 
-    pub fn load(path: &Path) -> Result<Self> {
+    pub fn load(path: &Path) -> Result<Self, FE> {
         let raw = Raw::load_file(path)?;
         let world_offset = match raw.find_str_backwards(Self::WORLD_TAG) {
             Some(offset) => offset,
-            None => return Err(anyhow!("no world found in file")),
+            None => return Err(FE::NoWorld),
         };
 
         let mut world_size: usize = 0;
         {
             let campaign = match raw.find_str(Self::CAMPAIGN_TAG, world_offset) {
                 Some(campaign) => world_offset + campaign,
-                None => return Err(anyhow!("no campaign found after world")),
+                None => return Err(FE::NoCampaign),
             };
 
             for i in (campaign - 256..campaign).rev() {
@@ -43,7 +42,7 @@ impl Save {
             }
         }
         if world_size == 0 {
-            return Err(anyhow!("Unable to determine world block size"));
+            return Err(FE::UnknownWorldSize);
         }
 
         let mut rd = ReadStream::new(&raw.mem, world_offset);
@@ -51,7 +50,7 @@ impl Save {
         Ok(Save { raw, world })
     }
 
-    pub fn save(&self, path: &Path) -> Result<()> {
+    pub fn save(&self, path: &Path) -> Result<(), FE> {
         let raw = {
             let mut wd = WriteStream::new(0);
             wd.write_ctx(&self.world, ())?;
diff --git a/src/fot/sgd.rs b/src/fot/sgd.rs
index d3996b8..749a9c5 100644
--- a/src/fot/sgd.rs
+++ b/src/fot/sgd.rs
@@ -1,8 +1,8 @@
 use super::decoder::Decoder;
+use super::ferror::FError as FE;
 use super::fstring::FString;
 use super::stream::{ReadStream, WriteStream};
 use super::tag::Tag;
-use anyhow::Result;
 use indexmap::IndexMap;
 
 #[derive(Debug)]
@@ -14,7 +14,7 @@ pub struct SGD {
 }
 
 impl Decoder for SGD {
-    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self> {
+    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self, FE> {
         let offset = rd.offset();
         let tag: Tag = rd.read()?;
         let unk1 = rd.read_bytes(0x48)?;
@@ -47,7 +47,7 @@ impl Decoder for SGD {
         })
     }
 
-    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
+    fn encode(&self, wd: &mut WriteStream) -> Result<(), FE> {
         wd.write(&self.tag)?;
         wd.write_bytes(&self.unk1);
 
diff --git a/src/fot/ssg.rs b/src/fot/ssg.rs
index a49fc2b..1a037c3 100644
--- a/src/fot/ssg.rs
+++ b/src/fot/ssg.rs
@@ -1,7 +1,7 @@
 use super::decoder::Decoder;
+use super::ferror::FError as FE;
 use super::stream::{ReadStream, WriteStream};
 use super::tag::Tag;
-use anyhow::Result;
 
 #[derive(Debug)]
 pub struct SSG {
@@ -10,13 +10,13 @@ pub struct SSG {
 }
 
 impl Decoder for SSG {
-    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self> {
+    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self, FE> {
         let tag: Tag = rd.read()?;
         let unk1 = rd.read_bytes(0x14)?;
         Ok(SSG { tag, unk1 })
     }
 
-    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
+    fn encode(&self, wd: &mut WriteStream) -> Result<(), FE> {
         wd.write(&self.tag)?;
         wd.write_bytes(&self.unk1);
         Ok(())
diff --git a/src/fot/stream.rs b/src/fot/stream.rs
index 1fc9c0b..2882b7e 100644
--- a/src/fot/stream.rs
+++ b/src/fot/stream.rs
@@ -1,7 +1,6 @@
 use super::decoder::{Decoder, DecoderCtx};
+use super::ferror::FError as FE;
 use super::raw::Raw;
-use anyhow::anyhow;
-use anyhow::Result;
 use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
 use std::io::Cursor;
 
@@ -37,10 +36,10 @@ impl<'a> ReadStream<'a> {
         &self.mem[self.offset()..]
     }
 
-    pub fn as_bytes(&mut self, size: usize) -> Result<&'a [u8]> {
+    pub fn as_bytes(&mut self, size: usize) -> Result<&'a [u8], FE> {
         if self.offset() + size > self.mem.len() {
             dbg!(self.offset(), size, self.mem.len());
-            Err(anyhow!("as_bytes/read_bytes size is bigger than buffer"))
+            Err(FE::StreamOverflow(self.offset(), self.size(), size))
         } else {
             let buf = &self.mem[self.offset()..self.offset() + size];
             self.skip(size);
@@ -48,7 +47,7 @@ impl<'a> ReadStream<'a> {
         }
     }
 
-    pub fn read_bytes(&mut self, size: usize) -> Result<Vec<u8>> {
+    pub fn read_bytes(&mut self, size: usize) -> Result<Vec<u8>, FE> {
         Ok(self.as_bytes(size)?.to_vec())
     }
 
@@ -58,35 +57,35 @@ impl<'a> ReadStream<'a> {
 
     // read_opt - decode with optional paramters. required for complex structure
     // with different origins (save / entfile) like entities
-    pub fn read_ctx<T: DecoderCtx<DCtx, ECtx>, DCtx, ECtx>(&mut self, ctx: DCtx) -> Result<T> {
+    pub fn read_ctx<T: DecoderCtx<DCtx, ECtx>, DCtx, ECtx>(&mut self, ctx: DCtx) -> Result<T, FE> {
         Ok(T::decode(self, ctx)?)
     }
 
-    pub fn read<T: Decoder>(&mut self) -> Result<T> {
+    pub fn read<T: Decoder>(&mut self) -> Result<T, FE> {
         Ok(T::decode(self)?)
     }
 
-    pub fn read_u8(&mut self) -> Result<u8> {
+    pub fn read_u8(&mut self) -> Result<u8, FE> {
         Ok(self.rdr.read_u8()?)
     }
 
-    pub fn read_bool(&mut self) -> Result<bool> {
+    pub fn read_bool(&mut self) -> Result<bool, FE> {
         Ok(self.read_u8()? != 0)
     }
 
-    pub fn read_u16(&mut self) -> Result<u16> {
+    pub fn read_u16(&mut self) -> Result<u16, FE> {
         Ok(self.rdr.read_u16::<LittleEndian>()?)
     }
 
-    pub fn read_i32(&mut self) -> Result<i32> {
+    pub fn read_i32(&mut self) -> Result<i32, FE> {
         Ok(self.rdr.read_i32::<LittleEndian>()?)
     }
 
-    pub fn read_u32(&mut self) -> Result<u32> {
+    pub fn read_u32(&mut self) -> Result<u32, FE> {
         Ok(self.rdr.read_u32::<LittleEndian>()?)
     }
 
-    pub fn read_f32(&mut self) -> Result<f32> {
+    pub fn read_f32(&mut self) -> Result<f32, FE> {
         Ok(self.rdr.read_f32::<LittleEndian>()?)
     }
 }
@@ -132,39 +131,39 @@ impl WriteStream {
         &mut self,
         val: &T,
         ctx: ECtx,
-    ) -> Result<()> {
+    ) -> Result<(), FE> {
         self.reserve(val.get_enc_size());
         val.encode(self, ctx)?;
         Ok(())
     }
 
-    pub fn write<T: Decoder>(&mut self, val: &T) -> Result<()> {
+    pub fn write<T: Decoder>(&mut self, val: &T) -> Result<(), FE> {
         self.reserve(val.get_enc_size());
         val.encode(self)?;
         Ok(())
     }
 
-    pub fn write_u8(&mut self, val: u8) -> Result<()> {
+    pub fn write_u8(&mut self, val: u8) -> Result<(), FE> {
         Ok(self.buf.write_u8(val)?)
     }
 
-    pub fn write_bool(&mut self, val: bool) -> Result<()> {
+    pub fn write_bool(&mut self, val: bool) -> Result<(), FE> {
         self.write_u8(val as u8)
     }
 
-    pub fn write_u16(&mut self, val: u16) -> Result<()> {
+    pub fn write_u16(&mut self, val: u16) -> Result<(), FE> {
         Ok(self.buf.write_u16::<LittleEndian>(val)?)
     }
 
-    pub fn write_i32(&mut self, val: i32) -> Result<()> {
+    pub fn write_i32(&mut self, val: i32) -> Result<(), FE> {
         Ok(self.buf.write_i32::<LittleEndian>(val)?)
     }
 
-    pub fn write_u32(&mut self, val: u32) -> Result<()> {
+    pub fn write_u32(&mut self, val: u32) -> Result<(), FE> {
         Ok(self.buf.write_u32::<LittleEndian>(val)?)
     }
 
-    pub fn write_f32(&mut self, val: f32) -> Result<()> {
+    pub fn write_f32(&mut self, val: f32) -> Result<(), FE> {
         Ok(self.buf.write_f32::<LittleEndian>(val)?)
     }
 }
diff --git a/src/fot/tag.rs b/src/fot/tag.rs
index 31ff898..988bf44 100644
--- a/src/fot/tag.rs
+++ b/src/fot/tag.rs
@@ -1,6 +1,6 @@
 use super::decoder::Decoder;
+use super::ferror::FError as FE;
 use super::stream::{ReadStream, WriteStream};
-use anyhow::Result;
 
 #[derive(Debug)]
 pub struct Tag {
@@ -9,13 +9,13 @@ pub struct Tag {
 }
 
 impl Decoder for Tag {
-    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self> {
+    fn decode<'a>(rd: &mut ReadStream<'a>) -> Result<Self, FE> {
         let name: String = rd.read()?;
         let version: String = rd.read()?;
         Ok(Tag { name, version })
     }
 
-    fn encode(&self, wd: &mut WriteStream) -> Result<()> {
+    fn encode(&self, wd: &mut WriteStream) -> Result<(), FE> {
         wd.write(&self.name)?;
         wd.write(&self.version)?;
         Ok(())
diff --git a/src/fot/world.rs b/src/fot/world.rs
index b14f0f3..1f14158 100644
--- a/src/fot/world.rs
+++ b/src/fot/world.rs
@@ -1,13 +1,12 @@
 use super::decoder::DecoderCtx;
 use super::entitylist::{EntityEncoding, EntityList};
 use super::esh::ESHValue;
+use super::ferror::FError as FE;
 use super::fstring::FString;
 use super::sgd::SGD;
 use super::ssg::SSG;
 use super::stream::{ReadStream, WriteStream};
 use super::tag::Tag;
-use anyhow::anyhow;
-use anyhow::Result;
 use deflate::deflate_bytes_zlib;
 use inflate::inflate_bytes_zlib;
 
@@ -30,7 +29,7 @@ pub struct World {
 impl World {
     const WORLD_HDR_LEN: usize = 0x13;
 
-    pub fn test(&mut self) -> Result<()> {
+    pub fn test(&mut self) -> Result<(), FE> {
         //let actor_type = self.entlist.get_type_idx("Actor").unwrap();
         //let ent = self.entlist.get_entity_mut(2122);
         let ent = self.entlist.get_entity_mut(2158);
@@ -68,7 +67,7 @@ impl World {
 
 pub type WorldOffsetSize = (usize, usize);
 impl DecoderCtx<WorldOffsetSize, ()> for World {
-    fn decode<'a>(enc: &mut ReadStream<'a>, ctx: WorldOffsetSize) -> Result<Self> {
+    fn decode<'a>(enc: &mut ReadStream<'a>, ctx: WorldOffsetSize) -> Result<Self, FE> {
         let offset = ctx.0;
         let size = ctx.1;
 
@@ -76,7 +75,7 @@ impl DecoderCtx<WorldOffsetSize, ()> for World {
         let uncompressed_size = enc.read_u32()?;
         enc.skip(4);
 
-        let data = inflate_bytes_zlib(enc.as_bytes(size)?).map_err(|e| anyhow!(e))?;
+        let data = inflate_bytes_zlib(enc.as_bytes(size)?).map_err(|e| FE::DeflateError(e))?;
         let mut rd = ReadStream::new(&data, 0);
 
         let mission: FString = rd.read()?;
@@ -101,7 +100,7 @@ impl DecoderCtx<WorldOffsetSize, ()> for World {
         })
     }
 
-    fn encode(&self, wd: &mut WriteStream, _: ()) -> Result<()> {
+    fn encode(&self, wd: &mut WriteStream, _: ()) -> Result<(), FE> {
         let data = {
             let mut wd = WriteStream::new(self.uncompressed_size as usize);