Volcanic Flail Snail

Amphibious. The volcanic flail snail can breathe air and water.

Antimagic Shell. The snail has advantage on saving throws against spells, and any creature making a spell attack against the snail has disadvantage on the attack roll. If the snail succeeds on its saving throw against a spell or a spell attack misses it, an additional effect might occur, as determined by rolling a d6:

1–2. If the spell affects an area or has multiple targets, it fails and has no effect. If the spell targets only the snail, it has no effect on the snail and is reflected back at the caster, using the spell slot level, spell save DC, attack bonus, and spellcasting ability of the caster.

3–4. No additional effect.

5–6. The snail’s shell converts some of the spell’s energy into an explosion of fire and destruction. Each creature within 30 feet of the snail must make a DC 15 Dexterity saving throw, taking 1d6 fire damage per level of the spell on a failed save, or half as much damage on a successful one.

Flail Tentacles. The flail snail has seven flail tentacles. Whenever the snail takes 20 damage or more on a single turn, one of its tentacles dies. If even one tentacle remains, the snail regrows all dead ones within 1d6 days. If all its tentacles die, the snail retracts into its shell, gaining total cover, and it begins wailing, a sound that can be heard for 600 feet, stopping only when it dies 5d6 minutes later. The added heat of the creature returning to its shell causes it to glow white hot. Healing magic that restores limbs, such as the regenerate spell, can halt this dying process.

Heated Body. A creature that touches the volcanic flail snail or hits it with a melee attack while within 5 feet of it takes 5 (1d10) fire damage.

Illumination. The volcanic flail snail sheds bright light in a 20-­foot radius and dim light for an additional 20 feet.

Water Susceptibility. For every 5 feet the elemental moves in water, or for every gallon of water splashed on it, it takes 1 cold damage.

Multiattack. The flail snail makes as many Burning Flail Tentacle attacks as it has flail tentacles, all against the same target.

Burning Flail Tentacle. Melee Weapon Attack: +5 to hit, reach 10 ft., one target. Hit: 6 (1d6 + 3) bludgeoning damage. If a creature or object hit by this attack is flammable, it ignites. A target that ignites takes 3 (1d6) fire damage at the start of each of its turns until a creature takes an action to douse the fire.

Incandescent Shell (Recharges after a Short or Long Rest). The snail’s shell emits dazzling, warm colored light until the end of the snail’s next turn. During this time, the shell sheds bright light in a 40-foot radius and dim light for an additional 40 feet, and creatures that can see the snail have disadvantage on attack rolls against it. In addition, any creature within the bright light and able to see the snail when this power is activated must succeed on a DC 15 Wisdom saving throw or be stunned until the light ends.

Shell Defense. The flail snail withdraws into its shell, gaining a +4 bonus to AC until it emerges. It can emerge from its shell as a bonus action on its turn.