Cheapest priced copy (Secret Lair Drop): $2.49 at Card Kingdom, near mint, their price list as of .
Mayael's Aria 
Enchantment · Rare · Alara Reborn · #121
At the beginning of your upkeep, put a +1/+1 counter on each creature you control if you control a creature with power 5 or greater. Then you gain 10 life if you control a creature with power 10 or greater. Then you win the game if you control a creature with power 20 or greater.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $2.49 to $7.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Double Masters 2022 | 253 | Rare | $2.79 | $2.99 |
| Double Masters 2022 | 524 | Rare | — | — |
| Alara Reborn | 121 | Rare | $2.79 | $7.99 |
| Secret Lair Drop | 1848 | Rare | $2.49 | — |
2 rulings from Wizards of the Coast
- 1 May 2009The three parts of the ability happen sequentially. For example, if you control a creature with 9 power when the ability starts to resolve, you'll put a +1/+1 counter on each creature you control — and now, since you control a creature with 10 power, you'll gain 10 life.
- 1 May 2009This ability triggers at the beginning of each of your upkeeps. Whether you control any applicable creatures is checked only when the ability resolves.