Cheapest priced copy (Adventures in the Forgotten Realms): $1.29 at Card Kingdom, near mint, their price list as of .
Guardian of Faith 
Creature — Spirit Knight · 3/2 · Rare · Adventures in the Forgotten Realms · #18
Flash
Vigilance
When this creature enters, any number of other target creatures you control phase out. (Treat them and anything attached to them as though they don't exist until their controller's next turn.)
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
7 printings · $1.29 to $29.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Adventures in the Forgotten Realms | 18 | Rare | $1.29 | $3.49 |
| Adventures in the Forgotten Realms | 362 | Rare | $3.99 | $8.99 |
| Adventures in the Forgotten Realms Promos | 18a | Rare | — | $29.99Out of stock |
| Adventures in the Forgotten Realms Promos | 18p | Rare | $9.99 | $10.99 |
| Adventures in the Forgotten Realms Promos | 18s | Rare | — | $6.99 |
| The List | AFR-18 | Rare | — | — |
| Secrets of Strixhaven Commander | 148 | Rare | $1.49 | — |
8 rulings from Wizards of the Coast
- 23 July 2021Phased out permanents are treated as though they don't exist. They can't be the target of spells or abilities, their static abilities have no effect on the game, their triggered abilities can't trigger, they can't attack or block, and so on.
- 23 July 2021Phasing out doesn't cause any "leaves the battlefield" abilities to trigger. Similarly, phasing in won't cause any "enters the battlefield" abilities to trigger.
- 23 July 2021Any continuous effects with a "for as long as" duration, such as that of Mind Flayer, ignore phased-out objects. If ignoring those objects causes the effect's conditions to no longer be met, the duration will expire.
- 23 July 2021Permanents phase back in during their controller's untap step, immediately before that player untaps their permanents. Creatures that phase in this way are able to attack and pay a cost of {T} during that turn. If a permanent had counters on it when it phased out, it will have those counters when it phases back in.
- 23 July 2021If an opponent gains control of one of your creatures, that creature phases out, and the duration of the control-change effect expires before it phases back in, that creature phases in under your control as that opponent's next untap step begins. If they leave the game before their next untap step, it phases in as the next untap step begins after their turn would have begun.
- 23 July 2021An attacking or blocking creature that phases out is removed from combat.
- 23 July 2021As a creature is phased out, Auras and Equipment attached to it also phase out at the same time. Those Auras and Equipment will phase in at the same time that creature does, and they'll phase in still attached to that creature.
- 23 July 2021Choices made for permanents as they entered the battlefield are remembered when they phase in.