Multiattack

The sleipnir makes two rune hooves attacks.

Rune Hooves

Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) bludgeoning damage and 3 (1d6) radiant damage. An undead creature who takes damage from this attack must succeed on a DC 16 Charisma saving throw or be restrained by magical runes until the end of its next turn.

Gold and Ice (1/Day)

The sleipnir summons a gilded avalanche in a 30-foot cone. Each creature in the area must make a DC 16 Dexterity saving throw. On a failure, a creature takes 13 (3d8) bludgeoning and 13 (3d8) cold damage, is pushed 15 feet away from the sleipnir, and is knocked prone. On a success, a creature takes half the damage and isn't pushed or knocked prone.