Backbite

You open a small portal between yourself and the attacker, and an exit portal just behind the attacker.  The portals remain open until the start of your next turn, granting you a +5 bonus to AC against that creature's attacks, including against the triggering attack.  If this causes the attack to miss you, then the attacking creature takes the attack's damage if the attack roll is equal to or greater than their AC.  Any subsequent attacks the creature makes that miss you while the portals are open are similarly redirected.  The portals automatically reposition themselves to interfere with and redirect the creature's attacks if you or they move.