Rukarazyll

Hybrid Nature. The rukarazyll has two types: elemental and fiend. It can be affected by a game effect that works on any of these creature types. Amorphous. The rukarazyll can move through a space as narrow as 1 inch wide without squeezing.

Nimble Elemental. The rukarazyll can take the Disengage action as a bonus action on each of its turns. Innate Spellcasting. The rukarazyll’s innate spellcasting ability is Intelligence (spell save DC 15). It can innately cast the following spells, requiring no material components:

At will: acid splash (3d6 acid damage), darkness, spike growth 3/day each: telekinesis, dominate beast (can target beasts and plants), mirror image

1/day each: blight, heal, wall of thorns

Shapechanger. The rukarazyll can use its action to polymorph into a Small or Medium beast or a commoner, or back into its true form. It retains its hit points, mental ability scores, alignment and personality. Its other game statistics are replaced by those of the chosen creature. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Multiattack. The rukarazyll makes three attacks: one with its bite and two with its tentacles.

Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 15 (2d8 + 6) piercing damage, plus 9 (2d8) acid damage. 

Tentacle. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 13 (2d6 + 6) bludgeoning damage plus 7 (2d6) acid damage. The target is poisoned and restrained by fungal growths entangling its body (escape DC 15). 

Pallid Infestation (disease). A target poisoned by a tentacle must make a DC 15 Constitution saving throw at the end of each of its turns. If the target succeeds on three of these saves, it is no longer poisoned and the infestation ends. Each time the target fails one of these saves, its Charisma score is reduced by 1d4. The target dies if this reduces its Charisma to 0. Otherwise, the reduction lasts until the target finishes a long rest. The body of a beast or humanoid that dies from this infestation collapses into a pile of fungus that can spread this disease for 7 days. Any creature that touches the fungus is poisoned and must make the saving throws.