Corrupted Giant Crab

Amphibious. The crab can breathe air and water.

Corrupted Aura. The corrupted energy radiating from the crab affects creatures within 10 feet of it. At the start of each of the crab's turns, each creature within 10 feet of the crab must make a DC 12 Wisdom saving throw or become frightened until the end of their next turn. If a creature's saving throw is successful, it is immune to the Corrupted Aura of all Corrupted Giant Crabs for the next 24 hours.

Reinforced Shell. When the Corrupted Giant Crab is subjected to a critical hit, it can use its reaction to roll a d6. On a 4 or higher, the critical hit becomes a normal hit instead.

Multiattack. The Corrupted Giant Crab makes two attacks: one with its Corrupted Bite and one with its Claw.

Claw. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit:  (1d6 + 1) bludgeoning damage, and the target is grappled (escape DC 11). The crab has two claws, each of which can grapple only one target.

Corrupted Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit:  (1d8 + 3) piercing damage. If the target is a creature, it must succeed on a DC 13 Constitution saving throw or be poisoned for 1 minute. While poisoned in this way, the creature takes 3 (1d6) necrotic damage at the start of each of its turns. The creature can repeat the saving throw at the end of each of its turns, ending the effect on a success. Poison does not stack.