Straight from the horse's mouth - the original material upon which this project is based, the multi-player online first person shooter released by Valve as part of the Orange Box: Team Fortress 2. Namely, the blog posts accompanying the game over the years across many updates, furnished with specially created art and gradually fully realised comics hosted on the official site.
Broader sites for the established canon. Shoutout to Jevilowo for doing such a thorough job documenting the timeline.
These particular entries in the TF2 canon do a fair bit of heavy-lifting in regard to where this project draws inspiration.
- Zepheniah's Ghost
- The introduction of Zepheniah's ghost as a Halloween game mechanic.
- Zepheniah's Will
- The Headless Horseless Horsemann
- The introduction of the Headless Horseless Horsemann (Silas Mann) as a Halloween game mechanic.
- Mann Family Photo
- A conspicuously torn photograph of the Mann family connected to the Horsemann's page, thought to be Gray's first appearance. Also the only image of Silas in the entirety of canon.
(That we know of.)
- Loose Canon
- The introduction of Radigan Conagher and Australium, the plot thread tying his work back to Dell and the Mann brothers.
- The Engineer Update
- Lots of little tidbits, including threads establishing the Classic engineer, Fred, as Dell's father.
- The Gunslinger
- The update where the Engineer, Dell Conagher, talks about sawing off his own arm in order to wield his grandfather's prosthetic.
- Blood Brothers
- The introduction of Gray Mann, and the subsequent death of his brothers.
- Coal Town
- Interesting point in the Hale family history. One of the barest glances we get at Bilious Hale's personality, outside of what Saxton says about his father.