A Compendium of Demons & the Nine Hells

Wondrous Item, Uncommon

This aged tome is bound in dark, weathered leather and reinforced with tarnished silver corners. Its pages contain detailed accounts of demons, the Nine Hells, infernal magic, and the many mortals who have encountered fiends throughout history.

The book contains anatomical sketches, arcane diagrams, eyewitness accounts, and handwritten notes from generations of demon hunters.

The majority of the surviving entries are attributed to the Order of Vereonor, an ancient order known as the Guardians, who devoted themselves to studying and combating fiends.

Inside the front cover is a simple inscription:

"Know the monster before you bargain with it."

Demonology

When you encounter a demon, you can spend 10 minutes outside of combat consulting the compendium. You have Advantage on the next Intelligence (Arcana) check you make to identify or learn information about that type of demon.

The DM determines what information the compendium contains. This information might include a demon's resistances, immunities, abilities, behaviour, tactics, or known weaknesses.

The compendium contains information about types of demons, rather than specific individuals, unless the individual has previously been documented within its pages.

Field Research

During combat, you can use an Action to rapidly search the compendium for information about a demon you can see.

Make an Intelligence (Arcana) check. The DC is determined by the DM based on how obscure the demon is.

On a success, the DM reveals one useful piece of information about the demon, such as one of its resistances, immunities, vulnerabilities, notable abilities, or behavioural traits.

On a failure, you find nothing useful before the opportunity passes.

Notable Entry: On the Futility of Poison

"We attempted to poison the creature through wine, blood, and finally a blade coated in nightroot extract. None produced the desired effect. The demon drank deeply and laughed."

"Do not waste venom upon that which was never truly alive."

Common poisons have no effect upon demons. Seek another means.

Notable Entry: The Order of Vereonor

The Order of Vereonor, known as the Guardians, devoted itself to the study, hunting, and containment of demons.

One surviving passage reads:

"Steel may wound the flesh. Fire may consume it. But light reminds the creature that it does not belong here."

The Order's records indicate that Radiant damage is particularly effective against many demonic entities, although individual demons may possess different resistances or immunities.

A handwritten note beneath the passage reads:

"When in doubt, bring the light."

Notable Entry: On Weaknesses

Weaknesses: None confirmed.

A later annotation has been added beneath the entry:

"Except, perhaps, turning down a good bargain."

The compendium records numerous instances of demons willingly entering dangerous situations because they believed they would gain something from the arrangement.

Desire, pride, ambition, vengeance, and greed are repeatedly identified as exploitable traits.

The final note reads:

"Remember: a demon that agrees to your terms has already decided what it intends to take from you."