Avoid Grievous Injury 2014

1st-level divination

Casting time: 1 reaction, which you take when you are struck by a critical hit
Range: Self
Components: V, S
Duration: instantaneous
Classes: Bard, Cleric, Druid, Sorcerer, Warlock, Wizard

You cast this spell when a foe strikes you with a critical hit but before damage dice are rolled. The critical hit against you becomes a normal hit.

Source: Deep Magic for 5th Edition (Kobold Press) · License: OPEN GAME LICENSE Version 1.0a details