Ability concept(no name yet...)

I was thinking yesterday about ...More specifically about his ult...And a idea hit me how cool would it be if Riot made a opposite of his ult. Thats when this concept hit me it would go well with some reworks and it would go perfectly with a demon or cursed character. So the idea is that when the champion gets low and has low hp like his opponent not same close i"d say (200 hp diff at max) He makes a link between himself and opponent that bonds them like a temporary oathsworn and while the link is up cca (3 to 5 sec u choose)any damage u take is also tranfered to ur enemy so he takes dmg also. Just imagine it like a bond if one champ dies so does the other.I think that would be great because it would force team to play as one and not rush or kills

P.S It would also be good as a item active ability but u decide Im free to any suggestion