Claw of Acamar - Eldritch Invocations

You can create a black, lead flail using your Pact of the Blade feature. The flail’s head is sculpted to resemble a pair of grasping tentacles. The weapon has the reach property. When you hit a creature with it, you can expend a spell slot to deal an additional 2d8 necrotic damage to the target per spell level, and you can reduce the creature’s speed to 0 feet until the end of your next turn