Beotodus

Frostblight. Whenever a creature takes cold damage from one of the beotodus attacks or is within 5 feet of the beotodus when it moves for the first time on its turn, it must succeed on a DC 17 Constitution saving throw or become afflicted with iceblight for 1 minute on a failed save. A creature that is resistant or immune to cold damage automatically succeeds on its saving throw.

Sensitive Ears. When a thunder spell is used within 60 feet of the beotodus while it is underground or partially submerged, it must make a DC 15 Constitution saving throw. On a failed save, the beotodus must immediately use its reaction to move toward the surface and fully emerged if it has the movement speed to do so. The beotodus automatically fails this saving throw if a sonic bomb is used within range of it.

Standing Leap. The beotodus' long jump is up to 30 feet and its high jump is up to 15 feet, with or without a running start.

Wade. The beotodus can partially submerge itself in snowy or icy terrain. While partially submerged, it has three-quarters cover (+5 bonus to AC and Dexterity saving throws) and can only use the following actions: Deadly Leap, Horn, and Slip 'n' Slide.

Multiattack. While above ground, the beotodus makes one Horn attack, one Tail attack, and one Hip Check. It can replace any attack with a Ice Chunk attack. While partially submerged, it uses Deadly Leap and makes one Horn attack.

Hip Check. Melee Weapon Attack: d20+8 to hit, reach 10 ft., one target. Hit: 23 (3d12 + 4) bludgeoning damage.

Horn. Melee Weapon Attack: d20+8 to hit, reach 10 ft., one target. Hit: 14 (3d6 + 4) piercing damage.

Ice Chunk. Ranged Weapon Attack: d20+8 to hit, reach 20/60 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage plus 4 (1d8) cold damage.

Tail. Melee Weapon Attack. d20+8 to hit, reach 10 ft., one target. Hit: 17 (3d8 + 4) bludgeoning damage.

Deadly Leap (Must be Partially Submerged). If the beotodus jumps at least 15 feet as part of its movement, it can then use this action to land partially submerged in a space that contains one or more other creatures. Each of those creatures must succeed on a DC 16 Strength or Dexterity saving throw (target's choice) taking 11 (2d6 + 4) bludgeoning damage plus 10 (3d6) cold damage and be knocked prone. On a successful save, the creature takes only half the damage, isn't knocked prone, and is pushed 5 feet out of the beotodus's space into an unoccupied space of the creature's choice. If no unoccupied space is within range, the creature instead falls prone in the beotodus' space.

Slip 'n' Slide (Recharge 5-6). The beotodus moves up to its speed, while spinning at an incredible speed. During this move, it can move through the spaces of other creatures without provoking opportunity attacks. Each creature the beotodus moves through must succeed on a DC 16 Dexterity saving throw or take 17 (3d8 + 4) bludgeoning damage plus 13 (3d8) cold damage and be knocked prone.

Snow Armor (3/day). While in snowy terrain, the beotodus can cover itself ina thick layer of snow. While covered snow, it gains a +2 bonus to its AC and it has resistance to bludgeoning damage. Additionally when a creature touches the beotodus or hits it with a melee attack while within 5 feet of it it must make a DC 17 Constitution saving throw or be afflicted with iceblight until the end of its next turn. Whenever the beotodus is subjected to fire damage there is a 50% chance that the snow armor melts, reducing its AC bonus by 1. Once its bonus AC from this effect is reduced to 0, the effect ends.

The beotodus can take 3 legendary actions, choosing from the options below.

Only one legendary action option can be used at a time and only at the end of another creature's turn. The beotodus regains spent legendary actions at the start of its turn.
Detect. The beotodus makes a Wisdom (Perception) Check.
Attack (Costs 2 Actions). The beotodus makes one Tail attack while on land, or one Horn attack while partially submerged.