The Eliacube

Indestructible
If any player would lose unspent mana at the end
of their turns, tap those mana sources. That
mana becomes mana of any color.
Pay 50 mana of any color: Search your library,
graveyard, hand and exile for Noximilien, the
Clockmaker and The Tragedy of Noximilien
and put them on the battlefield. Take an extra
turn after this one. If The Eliacube isn't in the
graveyard or exiled after the end of the extra
turn, you lose the game.