Keen Hearing and Smell. The wolf has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Pack Tactics. The wraith wolf has advantage on attack rolls against a creature if at least one of its allies is within 5 feet of the creature and the ally isn't incapacitated.

Ethereal Sight. The wraith wolf can see 60 ft. into the Ethereal Plane when it is on the Material Plane, and vice versa.

Incorporeal Movement. The wraith wolf can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

Draining Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (2d6 + 2) piercing damage. If the target is a creature, it must succeed on a DC 11 Strength saving throw or be knocked prone. On a successful bite, the wraith wolf recovers half the total damage as hp.

Drain Claw. Melee Weapon Attack: +8 to hit, reach 5 ft., one creature. Hit: 21 (4d8 + 4) necrotic damage. The target must succeed on a DC 16 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

Multiattack: Wraith wolf can perform two drain claw attacks or one Draining Bite and one drain claw.