(Twilight Coliseum isn't a spell.)
When Twilight Coliseum enters the battlefield, return a land you control to its owner's hand.
Green spells cost more to play.
: Add to your mana pool. If you played a land this turn, Add to your mana pool instead.
more to play.
: Add 
to your mana pool. If you played a land this turn, Add 
to your mana pool instead.
