The Columbian Exchange

{x}{w}{w}{t}: You and target opponent gain {x} life.
{x}{x}{u}{u}{t}: You and target opponent return exchange control of X non-land permanents.
{x}{x}{b}{b}{t}: X target creatures get -X/-X until end of turn, if you don't control any of the targeted creatures, you take X damage times 2.
{x}{x}{r}{r}{t}: Each opponent may take X damage, if they don't, you draw X cards for all damage avoided this way.
{x}{x}{g}{g}: Every player gets a 0/1 plant token with, "Sacrifice this creature, you may add {1} to y