mtg tree card Lifeswapping that's a fantastic precon upgrade sees 170% price spike put it into your hand MAGIC THE GATHERING MTG BLOOMBURROW

Even if you just tick it down to force some sacrifices and draw cards, thats killer on certain board states

If the greatest power among creatures you control is negative as this creature's ability resolves, X is considered to be 0

The classic is Dark Depths and Thespian's Stage, but theres likely better options these days

Lifegain is also technically a payoff but mostly it is an incidental one, it isn't a route to victory and shouldn't be the focus of a plan

Kaladesh had compounding factors, namely that energy was a complicated new mechanic with several costs having been misjudged, but had the designers been able to easily slap colored mana costs on most of the artifacts without tradition turning them away, things could have been different