Black Tendril Blade

You make a melee attack with a pact weapon against one creature within 5 feet of you. On a hit, the target suffers the weapon attack’s normal effects, and you can cause black tendrils to leap from the target to a different creature of your choice that you can see within 5 feet of it. The second creature takes necrotic damage equal to your spellcasting ability modifier.

This spell’s damage increases when you reach certain levels. At 5th level, the melee attack deals an extra 1d8 necrotic damage to the target on a hit, and the necrotic damage to the second creature increases to 1d8 + your spellcasting ability modifier. Both damage rolls increase by 1d8 at 11th level (2d8 and 2d8) and 17th level (3d8 and 3d8)