Cheapest priced copy (The List): $2.99 at Card Kingdom, near mint, their price list as of .
Azor's Gateway // Sanctum of the Sun 
Legendary Artifact // Legendary Land · Mythic · Rivals of Ixalan · #176
{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.
(Transforms from Azor's Gateway.)
{T}: Add X mana of any one color, where X is your life total.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $2.99 to $10.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The List | RIX-176 | Mythic | $2.99 | — |
| Rivals of Ixalan Promos | 176s | Mythic | — | $9.49 |
| Rivals of Ixalan | 176 | Mythic | $3.49 | $10.99 |
5 rulings from Wizards of the Coast
- 19 January 2018If a card in exile has {X} in its mana cost, X is considered to be 0.
- 19 January 2018The 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.
- 19 January 2018If an object has no mana cost, its mana value is 0. A mana value of 0 can still help unlock Azor's Gateway.
- 19 January 2018The ability of Sanctum of the Sun is a mana ability. It doesn't use the stack and can't be responded to.
- 19 January 2018The cards you exile from your hand are exiled face up.