Exanguinate

Extract the life energy from a foe and use it to heal yourself. A target that you can see within range must succeed a constitution saving throw or start having its blood and life energy drained by the spell. On a fail, blood magically emerges from the target's body, or if it doesn't have blood, life energy in the form of yellow-ish light (or whatever suits the creature better, to the DM's discretion) flows instead directly into you, dealing 3d6 necrotic damage to the target, healing you for that amount of hit points. Every time a target ends its turn being affected by the spell you deal an aditional 3d6 necrotic damage and heal that amount of hit points. On a save, the spell doesn't end and you can target a new creature as a bonus action on each of your turns until the spell ends.

At the begining of each of the target's turns it can make a Constitution saving throw, ending the effect on itself on a success. If a creature succeeds its saving throw against this spell, it has advantage on the next saving throw it makes againtst the same spell for the next 24 hours.

If a target that can bleed is targeted by this spell for the whole duration of the spell, it suffers one level of exhaustion.

At higher levels: If you cast this spell using a spell slot of 5th level or higher, the damage and healing increases in 1d6 for every slot level above 4th.