Monster's Hit Die

[ddobard1]

If a Caster wants to cast a spell like Cause Fear on a Monster must know Monster's Hit Die as the spell only affects creatures with 5 Hit Die or lower!
May the Caster deduce Monster's Hit Die from Monster's CR? Hit Die = CR? Ty.

[MrCow]

May the Caster deduce Monster's Hit Die from Monster's CR? Hit Die = CR?

This depends on the monster. Some generalizations:

• For humanoids: HD = CR
• For giants, aberrations, and monstrous humanoids: HD is often equal to CR, with some wiggle room
• For undead: Varies a lot. Generally low intelligence undead are around HD = CR * 2 with high intelligence undead around HD = CR.
• For elementals: Generally between HD = CR * 1.25 to HD = CR * 2.5. Elementals from older content tend to have higher HD compared to their CR.
• For outsiders: Depends on the specific outsider, but they are close to HD = CR (with some at HD = CR - 2)
• For oozes: Those with no intelligence tend to be around HD = CR * 1.5. Living spells are close to HD = CR