Inescapable Void

Whenever a player casts a spell, put a memory
counter on Inescapable Void, then that player
returns target non-land permanent he or she
controls to its owner's hand. If they can't,
sacrifice Inescapable Void.
When Inescapable Void leaves the battlefield,
each player may cast X spells from their hand
without paying their mana cost, where X is the
number of memory counters on Inescapable
Void.