Azor's Gateway // Sanctum of the Sun

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

Wotc — January 19, 2018

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.

Wotc — January 19, 2018

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

Wotc — January 19, 2018

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

Wotc — January 19, 2018

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

Wotc — January 19, 2018