Combine Vitality

You target up to 3 willing creatures in range. Upon casting, the hp of all the targets is added together into a health pool, if any creatures are missing hp, reduce the missing hp from the pools current hp.  Affected creatures do not fall unconscious until the pool is depleted, the spell ends.  When the spell ends, divide the damage missing from the pool between all affected creatures.

The pool cannot gain temporary hit points, and any temporary hit points present when the spell is cast are removed.