Market of Khe'chae

Whenever a player discards a card exile it under
Market of Khe'chae.
Fortified land gains "{t}: Each player secretly bids
{x} mana. Each player then pays that much mana.
The highest bidder can cast a spell under Market
of Khe'chae without paying it's mana cost."
Fortify {3} ({3}: Attach to target land you control.
Fortify only as a sorcery. This card enters the battlefield unattached and stays on the battlefield if
the land leaves.)