Zydar's Diagnostic

You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within reach. On a hit, the target suffers the weapon attack’s normal effects and arcane runes start appearing on the creature's weak spots. The next attack roll made against it before the end of your next turn has Advantage.

At 5th level, the melee attack deals an extra 1d8 radiant damage to the target on a hit. Damage rolls increase by 1d8 at 11th level and again at 17th level.