Blade Siphon

Your weapon becomes sheathed in black energy. As part of the action used to cast this spell, you must make a melee attack with a weapon against one creature within the spell's range, otherwise the spell fails.
On a hit, the target suffers the attack's normal effects, and it takes 1d6 necrotic damage as life force is pulled from their body. You heal a number of hit points equal to half the damage done by this spell (minimum 1).

At higher level

At 5th level, the melee attack deals an extra 1d6 necrotic damage to the target (2d6), damage increases by 1d6 at 11th level (3d6) and 17th level (4d6).