Multiattack

The rime worm makes two Rime Tendril attacks. It can replace one attack with a use of Freeze Prey.

Rime Tendril

Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 12 (2d6 + 5) bludgeoning damage plus 9 (2d8) cold damage. The target is grappled (escape DC 15) if it is a Medium or smaller creature and the rime worm doesn't have another creature grappled.

Freeze Prey

One creature grappled by the rime worm must succeed on a DC 15 Constitution saving throw or be petrified in ice for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. A petrified creature that takes fire damage has advantage on the saving throw.

Black Ice Spray (Recharge 5-6)

The rime worm sprays slivers of ice in a 30-foot cone. Each creature in the area must make a DC 15 Constitution saving throw, taking 36 (8d8) cold damage on a failed save, or half as much damage on a successful one. The area then becomes icy, difficult terrain for 1 minute.