Codex Ossium

Codex Ossium is a necromantic artifactand an Appendix Dungeon for Shadowdark and other classic fantasy systems. The Codex Ossium is a chained tome of vertebrae and leather that lets its owner assemble permanent skeletons, grow a cancerous bone annex beneath the earth, and whisper dark answers but at a price. Use the artifact alone or drop the included Annex of Bone onto any existing dungeon as a hostile side-complex with its own agenda.

Includes

The Codex Ossium ( Necromantic Artifact): binding rules, study requirements, minor and greater powers (e.g., Rite of Assembly for permanent skeletons), and escalating drawbacks (hunger, divine rebuke, sanctity restrictions, destruction conditions).

Annex of Bone (Annex Dungeon): a bone add-on lair run by Elias Coren and his skeletal retinue; gates, barricades, ambushes, and a  starved Giant Crab.

Composite skeleton rules: mix animal parts (bull skull charge, bear claws, goat legs, etc.) with tradeoffs to create weird, table ready undead.

Restoration track: recover missing folios to power up the Codex (stronger minions, expanding architecture, and maybe sentience).

Made for the Beyond Death Horror TTRPG Jam

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This adventure is released under Creative Commons CC0. All original writing, layout, and design are dedicated to the public domain. Use, remix, or republish freely. Cover background and background images  are excluded.  Some referenced mechanics (e.g., Shadowdark RPG) are under separate licenses  see the LICENSE file and PDF for full details.