Lake Troll

Amphibious. The lake troll can breathe air and water.

Keen Smell. The lake troll has advantage on Wisdom (Perception) checks that rely on smell.

Regeneration. The lake troll regains 10 hit points at the start of its turn. If the lake troll takes cold or fire damage, it regains only 5 hit points at the start of its next turn; if it takes both cold and fire damage, this trait doesn't function at the start of the lake troll's next turn. The lake troll dies only if it starts its turn with 0 hit points and doesn't regenerate.

Multiattack. The lake troll makes one bite attack and two claw attacks.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 9 (1d8 + 5) slashing damage.

Claws. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) piercing damage. If the lake troll hits a creature with both claw attacks in the same turn, the target creature must make a successful DC 16 Dexterity saving throw or its weapon (if any) gains a permanent and cumulative -1 penalty to damage rolls. If the penalty reaches -5, the weapon is destroyed. A damaged weapon can be repaired with appropriate artisan's tools during a long rest.