Got to make up a day, so let’s make a spell for a few different systems!
Conduit of Fate
1st-level enchantment
Casting Time: 1 action
Range: 30 feet
Components: V,S
Duration: concentration, up to one minute
You speak words of power and twin two willing souls together. Chose two willing creature in range. Those souls now share a total hit point pool. Damage to one deals damage to the whole hit point total. When the total hit point total is reduced to zero, both begin to die. When you heal one of the pair, increase the total hit point total by that much. When the spell ends, divide the remaining hit point total as equally as possible.
At Higher Levels: When you cast this spell using a spell slot of 2nd level or higher, increases the number of creatures included in the hit point pool by 1 for each slot level above 1st.
Conduit of Fate SPELL 1
Healing Enchantment
Traditions divine, primal
Cast [two-actions]
Range 30 feet; Targets 2 willing living creatures
You speak words of power and twin two willing souls together. Chose two willing creature in range. Those creatures now share a total hit point pool which is the sum of their hit points. Damage to one deals damage to the whole hit point total. When the total hit point total is reduced to zero, both begin to die as normal. When you heal one of the pair, increase the total hit point total by that much. When the spell ends, divide the remaining hit point total as equally as possible.
Heightened (+1) The number of creatures increase by 1.