Fire Sensitivity. While withing 5 feet of a flame, the Abyss Scurrier has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Thermoception: Abyss Scurrier see in heat signatures, they fear fire but are drawn to creatures.

Shadow Stealth. While in dim light or darkness, the demon can take the Hide action as a bonus action.

Claws. Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 10 (2d6 + 3) slashing damage or, if the Abyss Scurrier has advantage on the attack roll, 17 (3d6 + 3) slashing damage. 

Abyssal Corruption:  Every strike is infused with a dark, unknown poison, causing the victim of the strike to slowly loose their senses and eventually be taken over. Constitution Saving throw: DC (?)

Leaking Corruption: After being hit by an attack or spell the Abyss Scurrier's Corruption bursts from its body. Dexterity Saving Throw: DC (15), taking 1d10 on a fail and half on a success.