A Painsplit Champion?
In Pokemon, pain split is a move that essentially adds your health to your opponent's health, and then divides that by two. Then, it sets both of your health levels equal to that value.
This would be an interesting concept, possibly can be used on a tank to give a carry extra health, or used on a squishy to burst down their tanks.
Maybe on an item or an abillity?
) and also with Bond of Stone/Stoneborn Pact.