Multiattack

The rime worm makes two tendril attacks.

Tendril

Melee Weapon Attack. +8 to hit, reach 10 ft., one target. Hit: 8 (1d6 + 5) slashing damage. If both tendril attacks hit the same target in a single turn, that target is grappled (escape DC 15). The rime worm can grapple one creature at a time, and it can't use its tendril or devour attacks against a different target while it has a creature grappled.

Devour

Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 18 (2d12 + 5) slashing damage. If the target was grappled by the rime worm, it takes an additional 13 (2d12) cold damage.

Black Ice Spray (Recharge 5-6)

The rime worm sprays slivers of ice in a line 30 feet long and 5 feet wide. All creatures in the line take 26 (4d12) necrotic damage and are blinded; a successful DC 15 Constitution saving throw prevents the blindness. A blinded creature repeats the saving throw at the end of its turn, ending the effect on itself with a successful save.