Cave of Wonders

Yell — When Cave of Wonders enter's the battlefield, you may yell. If you do, Other lands
have Echo {1} until each card with "Cave" in it's
name leaves the battlefield.
Respond — When a player plays down a card with
Echo, spells in their hand have Landbound until
each card with "Cave" in it's name leaves the battlefield. (A card with Landbound has "To cast
this spell, instead of paying it's mana cost, tap X land
where X is this card's converted mana cost")