Eldritch Blade

You brandish the weapon used in the spell’s casting, enveloping it in an otherworldly glow and make a melee attack with it against one creature within 5 feet of you. On a hit, the target suffers the weapon attack’s normal effects and then becomes sheathed in ancient and esoteric energy until the start of your next turn. The next time the target is hit with a spell or weapon attack, the target suffers the attack's normal damage and effects, and takes an additional 1d6 cold, psychic, or radiant damage (your choice), and the spell ends.

This spell’s damage increases when you reach certain levels. At 5th level, the melee attack made as part of the spell's casting deals an extra 1d6 cold, psychic, or radiant damage (your choice) to the target on a hit, and the damage the target takes when hit by a spell or attack increases to 2d6. Both damage rolls increase by 1d6 at 11th level (2d6 and 3d6) and again at 17th level (3d6 and 4d6).