Vera's Vitriolic Veins

When you cast the spell, choose up to 4 creatures you can see within range to make dexterity saving throws (the targets can choose to fail). On a failure, a long, globous line of blood lashes out from you in their directions. When you cast this spell, and as an action on each turn thereafter, you can force all the tethered creatures to gain 4d8 hitpoints, and you lose the same amount. Alternatively, you can cause the creatures to take that much necrotic damage, and gain temporary hitpoints equal to half the total. On a successful save, the creatures take half damage, but suffer no additional effects.

Using a Higher-Level spell slot: when you cast this spell with a 6th level slot or higher, the number of creatures you can target increases by one.