If the exiled card is a land card, you may play it only if you have an available land play remaining this turn.

You may choose to discard your hand even if your hand contains zero cards.

If you cast a spell "without paying its mana cost," you can't choose to cast it for any alternative costs. You can, however, pay additional costs. If the spell has any mandatory additional costs, those must be paid to cast the spell.

Count the number of red mana symbols among the mana costs of permanents you control as Clive's triggered ability resolves to determine your devotion to red. If Clive is still on the battlefield at that time, it will be included in that count.

Clive's Hideaway's last ability only cares if you control four or more legendary creatures at the time it resolves. You don't even have to control four or more legendary creatures when you activate it.

If a spell has in its mana cost, you must choose 0 as the value of X when playing it without paying its mana cost.

Hybrid mana symbols, monocolored hybrid mana symbols, and Phyrexian mana symbols do count toward your devotion to their color(s).

Mana symbols in the text boxes of permanents you control don't count toward your devotion to any color.

"Hideaway N" means "When this permanent enters, look at the top N cards of your library. Exile one of them face down and put the rest on the bottom of your library in a random order. The exiled card gains ‘The player who controls the permanent that exiled this card may look at this card in the exile zone.'"

Any player who has controlled a permanent with a hideaway ability since a card was exiled with it may look at that card.

You play the card while Clive's Hideaway's last ability is resolving and still on the stack. You can't wait to play it later in the turn.

Colorless and generic mana symbols (, , , , , and so on) in mana costs of permanents you control don't count toward your devotion to any color.

If you put an Aura on an opponent's permanent, you still control the Aura, and mana symbols in its mana cost count towards your devotion. Similarly, if you make an opponent the protector of a Siege you control, mana symbols in that battle's mana cost count toward your devotion.