Keen Smell. The troll has advantage on Wisdom (Perception) checks that rely on smell.
Martial Advantage (1/Turn). The troll can deal an extra 7 (2d6) damage to a creature it hits with a melee attack if that creature is within 5 feet of an ally of the troll that isn't incapacitated.
Regeneration. The troll regains 10 hit points at the start of its turn. If the troll takes acid or fire damage, this trait doesn't function at the start of the troll's next turn. The troll dies only if it starts its turn with 0 hit points and doesn't regenerate.
Multiattack. The troll makes four attacks: one with its claw, one with its greataxe, and two with its bite.
Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 8 (1d6 + 4) piercing damage.
Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage. If the target is a creature, it must succeed on a DC 15 Constitution saving throw or be stunned until the start of the troll's next turn.
Greataxe. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 17 (2d12 + 4) slashing damage. If the target is a creature, it must succeed on a DC 15 Strength saving throw or be knocked prone.