Dawnfly, Desolation Nymph

Limited Amphibiousness. Can breathe air and water but needs to be submerged at least once every 4 hrs to avoid suffocating.

Shifting Camouflage. Its carapace adapts to its current surroundings. The nymph has advantage on Dex (Stealth) checks made to hide in nonmagical natural terrain.

Hinged Maw. Melee Weapon Attack: +5 to hit, 15 ft., one creature,. 14 (2d10+3) piercing damage. If the target is a Med or smaller creature it is grappled (escape DC 13) and pulled to within 5 ft. of the nymph. Until this grapple ends the target is restrained and the desolation nymph can't use its Hinged Maw on another target.

Swallow. The desolation nymph makes one Hinged Maw attack vs. a Med or smaller target it is grappling. If the attack hits the target is also swallowed and the grapple ends. While swallowed the target is blinded and restrained it has total cover vs. attacks and other effects outside the nymph and it takes 7 (2d6) acid at the start of each of the nymph's turns. The nymph can have only 1 foe swallowed at a time. If the desolation nymph dies a swallowed creature is no longer restrained by it and can escape from the corpse using 5 ft. of movement exiting prone.

Water Jet. Takes the Disengage action and each creature within 5 ft. of nymph: DC 13 Dex save or be blinded until end of its next turn.