Von Carstein's Vampiric Ray

You create an emerald beam of Necromantic energy that flies from your hand and corrupts your target and then pulls the residual energy back into you. Make a ranged spell attack against a target you can see. On a hit, that target takes 6d10 necrotic damage, and you learn all of its damage resistances and vulnerabilities.

While concentrating on the spell, you can use a bonus action on each of your subsequent turns to deal an additional 1d10 necrotic damage to your target, and gain temporary hit points equal to half of the damage dealt.

At higher levels: For each level, you cast this spell of 6th and above, the initial damage increases by 1d10.