Necrochronica

At the beginning of each player's upkeep,
that player places a time counter on
Necrochronica. Then that player may discard
a card. Then if Necrochronica has 6 time
counters on it, you may remove 4. If you do,
all players may move their commander from
their command zone to their graveyard. If it
has 12, move all commander cards from
graveyards, command zones, and battlefields
to the battlefield under Necrochronica's
owner's control and exile Necrochronica.