Let’s get caught up with an idea from a 5e game.

 

Devil, Diabolical Tutor

Tiny fiend(devil, shapechanger), lawful evil

Armor Class 9

Hit Points 10 (3d4+3)

Speed 20 ft.

STR	DEX	CON	INT	WIS	CHA
6 (-2)	16 (+3)	12 (+1)	18 (+4)	12 (+1)	16 (+3)

Skills Deception +5, Insight +3, Persuasion +5, Arcana +5, Religion +5, History +5,Nature +5

Damage Resistances fire, piercing, bludgeoning, and slashing from nonmagic weapons that are not silvered

Senses passive darkvision 120 ft., Perception 11

Languages infernal, Common

Challenge 1 (200 XP)

Special Traits

 

• Shapechanger: The diabolical tutor can use its action to polymorph into a beast form that resembles a rat (speed 20 ft.), a raven (20 ft., fly 60 ft.), or a spider (20 ft., climb 20 ft.), or back into its true form. Its statistics are the same in each form, except for the speed changes noted. Any equipment it is wearing or carrying isn’t transformed. It reverts to its true form if it dies.
• Devil’s Sight: Magical darkness doesn’t impede the diabolical tutor’s darkvision.
• Magic Resistance: The diabolical tutor has advantage on saving throws against spells and other magical effects.
• Dark Knowledge: When you spend an action to make a knowledge check and consult the diabolical tutor, you may add the diabolical tutor’s bonus to these checks to your own.Actions

 

• Bite: Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 2 (2d4 – 2) piercing damage.

 

Description

A man-shaped monster that stinks of brimstone and rot but offers fel knowledge to any who listen to its evil lips.