Tentacruel (5e Creature)
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Medium elemental, any alignment
Saving Throws Con +8, Wis +4
Rain Dish. While submerged in water or outside during rain while it has at least 1 hit point, the tentacruel regains 10 hit points at the start of each of its turns.
Clear Body. The tentacruel is immune to any effect that would cause it to gain disadvantage on attack rolls, ability checks, or saving throws.
Liquid Ooze. When the tentacruel takes damage of any type but psychic, each creature within 5 feet of the tentacruel takes 7 (2d6) poison damage.
Hydro Pump. Ranged Spell Attack: +8 to hit, range 60/180 ft., one target. Hit: 15 (3d6 + 5) bludgeoning damage. If the target is a creature, it must succeed on a DC 16 Strength saving throw or be pushed back 10 ft.
Sludge Wave (Recharge 5-6). The tentacruel releases a wave of poison in a 30 foot radius around it. All creatures within that area must succeed on a DC 16 Constitution saving throw or take 18 (4d8) poison damage. A creature that fails this save by 5 or more is also poisoned for 1 minute. A poisoned target can repeat the saving throw at the end of each of its turn, ending the effect on a success.