Calcification

*When you first learn this spell, You must roll 2d20's with disadvantage, take the sum of these two rolls and write it down somewhere so you don't forget it, as a creature must be missing at least that much hp for this spell to be cast on them, or you can alter cast it by destroying the animate undead skeleton creature* 

When you cast this spell, you manipulate the targets bones, forcing them to rapidly grow covering the creature in a hard shell made of their own bones. (this spell can't be cast on boneless creatures) 
This Spell Grant's the target 4d8 temporary hit points, these temporary hit points are effected by the creatures resistances and vulnerability's like normal, while a creature has these temporary hit points, their movement speed is reduced by 5FT, but any melee attackers that would hit this creature, take 2d4 Piercing damage in recoil. once these hit point's are gone, the spell ends. 

*for each level this spell is cast above level 4, increase the amount of d8's one dice and give the piecing damage a +2 (for example, casting this as a level 5 spell would grant the target 5d8 temporary hit points and they would deal 2d4+2 piercing damage)*