I was thinking shield save you form a strike, but what about a spell that saves you from a crit?
Strike Break
1st-level abjuration
Casting Time: 1 reaction
Range: 30 feet
Components: V, S
Duration: instantaneous
An field of magic force stops a strike from decimating a target, but merely causes the target to be pummeled. When you cast this spell, a target in range is no longer subject to a critical hit, but is struck as normal with an attack or spell. This will only affect one strike even if the target is struck with multiple critical hits in a round.
Thoughts?
Throat Punch Games 