Fell Turtle (5e Creature)
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Medium undead, chaotic evil
Snap. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) piercing damage
Withdraw. It can withdraw its arms, legs, and head into its shell as a reaction. While it is withdrawn, it gains a +5 bonus to AC and is immune to any effect that would move it, but it cannot move or perform any actions, and it can only see in front. It may exit its shell as a bonus action.
A facetiously sturdy-looking discolored turtle, rumored to be the agglutination of many a dead turtle. It hides a ridiculously powerful jaw and a rather low tolerance for damage.