Horse, Vampiric (5e Creature)
From D&D Wiki
Large undead, unaligned
Skills Perception +6
Undead Fortitude. If damage reduces the horse to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the horse drops to 1 hit point instead.
Regeneration. The horse regains 13 (2d6 + 3) hit points and the start of his turn if he has at least 1 hit point and isn't in sunlight. He may spend 1 spirit point when this happens to double the hit points regained. If the horse takes radiant damage, this trait doesn't work until the start of his next turn. When he is reduced to 0 hit points, he may spend 1 spirit point to remain at 1 hit point instead. If it would be killed, it must spend 2 spirit points and become incapacitated until the end of his next turn.
Sunlight Hypersensitivity. The zombie takes 7 (2d6) radiant damage at the beginning of each turn he starts his turn in sunlight, or when it enters direct sunlight.
Trample. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 30 (4d12 + 4) piercing damage and the zombie regains a number of hit points equal to the damage dealt. If a creature is killed by this attack, they are raised as an Undead under their control after 1 minute. These creatures retain the same stats as when they were alive, except their type changes to Undead, they gain dark vision for 60 ft. unless they had better, and their unarmed attacks gain this effect, but not this attack itself. If damage reduces the them to 0 hit points, they must make a DC 5 + damage taken Constitution saving throw, unless the damage is radiant damage or from a critical hit. On a success, they drop to 1 hit point instead. These minions will always stay under your control until they die and control over your minions cannot be taken from you.
Even a typical riding horse can become a beastly foe after exposure to the stone mask.