Claw Strike

As an action, you can summon a Chiropteran claw out of your right hand, which grows to roughly 1.5x the normal size of your hand. It is considered magical. It can be used to melee attack (using spell attack modifier) that deals 1d8 slashing and 1d4 necrotic damage (lvl 10 - 1d10/1d6 lvl 14 - 2d6/1d8  level 18 - 2d8/1d10). You are proficient with your claw. After you cast a spell (but not a cantrip!), you can summon the claw as a bonus action instead. As long as the claw is out you can attack with it as a bonus action.

In addition you can use the claw to make attacks of opportunity when it is already out. Whenever you do so you can cast a cantrip as part of the same reaction.