Rime Worm

Amphibious. The rime worm can breathe air and water.

Icy Body. A creature that touches the rime worm or hits it with a melee attack while within 5 feet of it takes 4 (1d8) cold damage.

Snow Camouflage. The rime worm has advantage on Dexterity (Stealth) checks made to hide in snowy terrain.

Snow Stride. The rime worm can burrow through nonmagical snow and ice in addition to sand, earth, and mud. In addition, difficult terrain composed of snow or ice doesn't cost it extra movement.

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.