Quicksilver Sea

If you cast a card without paying its mana cost, you can’t choose to cast it for any alternative costs, such as evoke or the alternative cost provided by the morph ability. If it has {X} in its mana cost, X must be 0. However, you can pay optional additional costs, such as kicker, and you must still pay mandatory additional costs, such as the one on Fling.

If you reveal a land card when resolving the chaos ability, you may play it only if you haven’t played a land yet that turn.

You play the card (meaning it play it if it’s a land card or cast it if it’s a nonland card) as part of the resolution of the chaos ability. Timing restrictions based on the card’s type are ignored. Other restrictions, such as “Cast [this card] only during combat,” are not.