| Type: Codex of magical research |
| Type of magic: Unholy |
| Levels of research: 3 |
The Fiendish Codex explains a number of well known aspects of demons, including their physiology, their interactions on the Material Plane, the roles they fit into, and how possession works.
| Spell: Fiendish Magic - Gain the “Repair Fiend” healing spell. |
| Proficiency: Arcane Knowledge - Gain +2 to Knowledge(Arcane) |
| Mount: Hellfire Horse - Gain the “Summon Fiendish Steed” Ritual. |
| Spell: Unholy Sight - Gain the Detect Good consequence spell - Detects Celestials, Lawful Paladins and Good Clerics. |
| Proficiency: Improved Arcane Knowledge - Gain +1 to Knowledge(Arcane) |
| Unholy Communion - Gain access to Fiendish Pacts. |