Bleeding Armor

Summon a swarm of spectral bats out of blood magic to defend yourself. Any enemies who make a melee attack against you or are within 5 feet of you take 2d4 piercing damage. Ranged attacks have disadvantage. You gain a +5 to your AC, and every attack that misses slashes away at the bats and decreases AC by 1. While Bleeding Armor is active, you can use your swarm of spectral bats to teleport up to 10 feet away in an unoccupied space as a reaction. If you do this, Bleeding Armor is dispelled and releases a blast in a 10 ft radius of you. Creatures must make a DEX saving throw, or take 3d10 force damage, and half as much on a success. 

At higher spell levels, the bats do an extra 1d4 damage and the bonus AC increases by 1.