Bloodstar

You conjure a magical construct called a bloodstar to lash out and greivously wound your enemies. It has AC 10 + spellcasting modifier, 5x the spell level of hit points, and immunity to psychic and poison damage. It pulses with a 20ft radius of dim ruby light. You may move the bloodstar anywhere within range using an action to concentrate on the new space.

Any creature you designate within 10 feet of the bloodstar that takes damage from any source other than the bloodstar must make a CON save against your spell save DC. On a failed save, the victim takes 2d8 necrotic damage as their vulnerability gives way to the siphoning of their life energy. Their blood appears to be streamed into the bloodstar.
Each time a victim or victims are damaged, a new save is allowed.

At higher levels, the damage dealt increases by 1d8 per spell level above 4th.

(revised from 3.5e)