Frostmare (5e Creature)
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Large elemental, lawful neutral
Chill Aura. The frostmare freezes liquids within 10 feet of it, allowing it to walk on water and other substances.
Confer Cold Resistance. The frostmare can grant resistance to cold damage to anyone riding it.
Rejuvenation. If the frostmare's frost-heart is intact, a destroyed frostmare gains a new body in 1d10 days, regaining all its hit points and becoming active again. The new body appears within 5 feet of the frost-heart.
Hooves. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage plus 7 (2d6) cold damage.
Chill Step. The frostmare can move it, and any creature riding it, up to 30 feet in any direction as long as it doesn't end in anything solid, or fire. If it passes through a creature, the creature takes 7 (2d6) cold damage.
A frostmare appears as a large semi-transparent, blue-white horse with a mane and tail of animate ice. Its eyes glow a bright white, and the area around it is chilled.
Elemental Steed. A frostmare is created through a 1-hour ritual requiring the conjure minor elementals spell, a pool of water at least 10 feet long and 3 feet deep, and a diamond worth at least 300 gp. The water and diamond are consumed leaving behind a large crystal called a frost-heart. The frost-heart summons forth the frostmare, and if the frost-heart is destroyed, the frostmare is destroyed as well.
Loyal to the Holder. The frostmare serves whoever holds the frost-heart that created it. As such, many spellcasters create frostmares and sell the frost-hearts to nobles and criminals. Similarly, anyone that can claim a frost-heart earns the services of the frostmare that it is bound to.
Elemental Nature. A frostmare doesn't require air, food, drink, or sleep.