Cheapest priced copy (Tales of Middle-earth Commander): $0.99 at Card Kingdom, near mint, their price list as of .
Arboreal Alliance 
Enchantment · Rare · Tales of Middle-earth Commander · #497
When this enchantment enters, create an X/X green Treefolk creature token.
Whenever you attack with one or more Elves, populate. (Create a token that's a copy of a creature token you control.)
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $0.79 to $1.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Tales of Middle-earth Commander | 497 | Rare | $0.99 | $0.79 |
| Tales of Middle-earth Commander | 541 | Rare | — | $1.49 |
8 rulings from Wizards of the Coast
- 3 November 2023Arboreal Alliance's last ability triggers whenever you attack with at least one Elf. You populate exactly once as it resolves, no matter how many Elves you attacked with.
- 3 November 2023If Arboreal Alliance enters the battlefield without being cast, or if you cast it with X equal to 0, you'll create a 0/0 green Treefolk creature token. Unless something else is raising its toughness, it will immediately die.
- 12 January 2024If you choose to copy a creature token that's a copy of another creature, the new creature token will copy the characteristics of whatever the original token is copying.
- 12 January 2024Populate doesn't target the creature token you're copying. You choose that creature token as you're taking the populate action. You can choose any creature token you control. If a spell or ability causes you to create a creature token and then instructs you to populate, you may choose to copy the token you just created, or you may choose to copy another creature token you control.
- 12 January 2024If you control no creature tokens when you populate, nothing will happen.
- 12 January 2024Any enters-the-battlefield abilities of the copied token will trigger when the new token enters the battlefield. Any "as [this creature] enters the battlefield" or "[this creature] enters the battlefield with" abilities of the copied token will also work.
- 12 January 2024The new creature token copies the characteristics of the original token as stated by the effect that created the original token.
- 12 January 2024The new token doesn't copy whether the original token is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any noncopy effects that have changed its power, toughness, color, and so on.