Diffindo

You point at a single target with your spellcasting focus, and make a slashing pattern with it, saying "Diffindo"  of energy attack and carves into its flesh in the same pattern you inscribed in the air. The target must make a Constitution saving throw. On a failed save, the creature receives 1+ your spellcasting ability modifier slashing damage, as the spell carves shallow wounds that keep bleeding until they are closed. Whenever injured this way, the target receives 1+ your spellcasting ability modifier each round. At the end of their turn they remake the saving throw. The creature keeps bleeding until it passes it's save, is killed, or is treated with a successful Medicine check, with a DC equal to your Saving throw, a Lesser or Greater restoration, or. If the target drops to 0 hit points this way, the bleeding causes Disadvantage on the Death saves unless they regained any hit points before going down.

This spell can be used to damage items that can be by damaged via slashing damage, but cannot sever limbs.

If the target succeeds on the saving throw, it receives half damage and no other effect. A non-bleeding creature, such as a construct or a skeleton, or a creature with heavy armor automatically succeeds the save.

You cannot learn this spell from leveling up or class features, you must re-invent/re-discover it or be granted/take it from another.