Vampiric Retreat

You teleport to an ally up to 30ft away from you, leaving a dark mist in a 5ft radius in the space you once were. Creatures in that area must make a CON save. They take half damage on a success and a full 2d8 necrotic damage on a fail.
When you reach your ally, if your HP is (numerically) lower than theirs you heal half the damage given. If your ally has less HP than you (numerically), they heal all the damage given.

When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d8 for each slot level above 2nd.