As soon as Jace laid eyes on the great sphinx's chamber, the shards of memory began sliding into place.

Azor's Gateway // Sanctum of the Sun

(Transforms from Azor's Gateway.)
{T}: Add X mana of any one color, where X is your life total.

{1}, {T}: Draw a card, then exile a card from your hand. If cards with five or more different mana values are exiled with Azor's Gateway, you gain 5 life, untap Azor's Gateway, and transform it.

The List

Rivals of Ixalan Promos

Rivals of Ixalan

{1}, {T}: Draw a card, then exile a card from your hand. If cards with five or more different converted mana costs are exiled with Azor's Gateway, you gain 5 life, untap Azor's Gateway, and transform it.

For more information on double-faced cards, see the Ixalan mechanics article (http://magic.wizards.com/en/articles/archive/feature/ixalan-mechanics).

If a card in exile has {X} in its mana cost, X is considered to be 0.

If an object has no mana cost, its mana value is 0. A mana value of 0 can still help unlock Azor’s Gateway.

The ability of Sanctum of the Sun is a mana ability. It doesn’t use the stack and can’t be responded to.

The cards you exile from your hand are exiled face up.

The mana value of a split card, such as a card with aftermath from the Amonkhet block, is based on the combined mana cost of its two halves. A split card doesn’t have two mana values.