Regeneration: Regain 10hp at the start of its turn. If it takes any fire or acid damge in the previous turn, this trait does not function at the start of its turn. The Wolf Troll dies if it starts a turn with 0hp or less and doesn't regenerate.
Pack Tactics: Wolf Troll has advantage on all rolls if within 30" of another Wolf Troll
Bite: +6 2d8+3 piercing damage, target makes DC 13 constitution save or be poisoned until the end of next turn
Negation: As a reaction if the Wolf Troll or an ally within 30" takes damage, the Wolf Troll can use its negation ability to attempt to negate the damage. An opposed attack roll is made against the attack roll and if the Wolf Troll wins no damage is dealt to the Wolf Troll or one ally within 30". Magic attacks that do not require savings throws can be avoided with an opposed roll against the equivalent caster attack roll.