Blighted Mount

The first time you cast this spell, you call forth the undead spirit of a legendary horse and have it possess the corpse of an equestrian creature that you can see within range. Subsequent casts will simply resummon the fully formed horse in an empty space that you can see within range. The corpse then takes on the form of a Blight Horse and will obey your commands. This creature cannot take the attack action and during combat this creature cannot be commanded and will only take the dodge action (Unless the creature is being actively ridden). The creature disappears in a puff of smoke if hit by any attack, and leaves behind any objects it was carrying. Otherwise, this creature lasts until  dismissed by the caster.

At Higher Levels.  When you cast this spell using a spell slot of 4th level or higher, the horse will function as normal, however the creature is now an ally to you, can be commanded during combat, and is allowed to take the attack in and out of combat. This version of the horse lasts 8 hours or until the horse's hitpoints reach zero. Casting this spell at 4th level or higher requires reins taken off a dead horse, this item is consumed by the spell.