Soothsayer's Shield 2014

2nd-level divination

Casting time: 1 reaction, when you are hit by an attack
Range: Self
Components: V, S
Duration: instantaneous
Classes: Bard, Cleric, Druid, Ranger

This spell can be cast when you are hit by an enemy's attack. Until the start of your next turn, you have a +4 bonus to AC, including against the triggering attack.

Source: Deep Magic Extended (Kobold Press) · License: OPEN GAME LICENSE Version 1.0a details