Nymphernal (5e Creature)
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Medium monstrosity, unaligned
Hold Breath. While out of water, the nymphernal can hold its breath for 24 hours.
Sneak Attack (1/Turn). The nymphernal deals an extra 5 (2d4) damage when it hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of the nymphernal that isn't incapacitated and the nymphernal doesn't have disadvantage on the attack roll.
Water Breathing. The nymphernal can only breathe underwater.
Bite. Melee Weapon Attack: +5 to hit, reach 10 ft., one target. Hit: 25 (4d10 + 3) piercing damage.
These creatures are the result of the unnatural fusion between a humanoid and a dragonfly nymph. The nymphernal's slothful movement and equally sluggish metabolism allow it to survive for extended periods between meals, often concealing itself in an algae-choked pool or a wet treefall pit until prey blunders within striking distance of its highly modified lower jaw. This deadly appendage can lash out with enough force to punch neatly through the torso of the average humanoid prey, or even shatter armor plating in a single blow. Like its arthropod base, the nymphernal breathes in aquatic environments through its anal opening, and can force water from the orifice to propel itself in short bursts. So long as it retains a water supply in its abdomen, it can function on land for several days at a time.