Elemental, Permafrost

Earth Glide. Can burrow through nonmagical unworked earth/stone with o disturbing material it moves through.

Elemental Nature. Doesn't require air food drink or sleep.

Frigid Footprints. The ground within 10 ft. of the permafrost elemental freezes over and is difficult terrain.

Plague Bearer. If it takes 15+ fire on single turn each creature within 10 ft. of it: infected with primordial plague disease (DC 14 Con negates). Alternatively creature becomes infected with sewer plague or cackle fever (elemental's choice) instead. Primordial plague takes 1 min to manifest in infected creature. After 1 min creature poisoned until disease cured. Every 24 hrs that elapse creature must re-save reducing its hp max by 5 (1d10) on failure. Disease is cured on success. Reduction lasts until disease is cured. Creature dies if disease reduces its hp max to 0.

Multiattack. Two Slam attacks.

Slam. Melee Weapon Attack: +7 to hit, 10 ft., one target, 13 (2d8+4) bludgeoning damage + 7 (2d6) cold.

Plague-Ridden Pound (Recharge 5-6). Brings both of its fists down striking ground and sending ice shards from its body flying at nearby creatures. Each creature on the ground within 20' of it: 10 (3d6) bludgeoning damage and 10 (3d6) cold knocked prone and becomes infected with primordial plague (see Plague Bearer; DC 14 Dex half damage and not prone or infected).