Death Burst. When the rime hulk dies, it explodes in a 10-foot-radius sphere of frigid air and frost centered on itself. Each creature in that area must succeed on a DC 15 Constitution saving throw or take 10 (3d6) cold damage.
Multiattack. The rime hulk makes two Slam attacks.
Slam. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit:9 (1d10 + 4) bludgeoning damage plus 9 (2d8) cold damage.
Trail of Frost (Recharge 5–6). The rime hulk moves up to its speed without provoking opportunity attacks and can move through the space of any Medium or smaller creature. Each time the rime hulk enters another creature's space for the first time during this move, that creature must make a DC 15 Constitution saving throw. On a failed save, the creature takes 22 (4d10) cold damage, and its speed is reduced by 10 feet until the start of the rime hulk's next turn. On a successful save, the creature takes half as much damage only.
Rime hulks are a withered branch of the frost giant family tree, descended from ancient giants who withdrew from the world and succumbed to their elemental nature. Most rime hulks dwell in the Frostfell, the "plane of ice" that forms the border between the Elemental Planes of Air and Water. Others lurk in isolated rifts in enormous polar glaciers.