Grand Ossuary (OVER-017) - Planechase 2012 Planes

Whenever a creature dies, its controller distributes a number of +1/+1 counters equal to its power among any number of target creatures they control.
Whenever chaos ensues, each player exiles all creatures they control and creates X 1/1 green Saproling creature tokens, where X is the total power of the creatures they exiled this way. Then planeswalk.