Cheapest priced copy (Fallout): $5.99 at Card Kingdom, near mint, their price list as of .
Mantle of the Ancients 
Enchantment — Aura · Rare · Forgotten Realms Commander · #277
Enchant creature you control
When this Aura enters, return any number of target Aura and/or Equipment cards from your graveyard to the battlefield attached to enchanted creature.
Enchanted creature gets +1/+1 for each Aura and Equipment attached to it.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
7 printings · $5.99 to $14.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Forgotten Realms Commander | 8 | Rare | $8.49 | — |
| Forgotten Realms Commander | 277 | Rare | $11.99 | — |
| Fallout | 165 | Rare | $5.99 | $10.99 |
| Fallout | 452 | Rare | $8.49 | $13.99 |
| Fallout | 693 | Rare | — | $14.99 |
| Fallout | 980 | Rare | — | $12.99 |
| Wilds of Eldraine Commander | 70 | Rare | $7.99 | — |
3 rulings from Wizards of the Coast
- 23 July 2021As the enters-the-battlefield ability is resolving, any targets that couldn't be legally attached to the creature enchanted by Mantle of the Ancients stay in your graveyard.
- 23 July 2021If Mantle of the Ancients becomes attached to a different creature in response to its enters-the-battlefield ability, the creature it's attached to as that ability is resolving is the "enchanted creature," even though you used the original enchanted creature to choose targets. This means some of those targets may become illegal.
- 23 July 2021If Mantle of the Ancients leaves the battlefield before its enters-the-battlefield ability resolves, the last permanent it was attached to before leaving the battlefield is the "enchanted creature" (even if that permanent is no longer a creature).