Cheapest priced copy (Avatar: The Last Airbender Eternal): $6.99 at Card Kingdom, near mint, their price list as of .
Agent of Treachery 
Creature — Human Rogue · 2/3 · Rare · Core Set 2020 · #43
When this creature enters, gain control of target permanent.
At the beginning of your end step, if you control three or more permanents you don't own, draw three cards.
Legal inCommanderPioneerModernLegacyVintage
Banned inBrawl
Not legal inStandardPauper
5 printings · $6.99 to $16.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Core Set 2020 | 43 | Rare | $8.99 | $12.99 |
| Core Set 2020 Promos | 43p | Rare | $8.99 | $12.99 |
| Core Set 2020 Promos | 43s | Rare | — | $16.99 |
| Secret Lair Drop | 2005 | Rare | $12.99 | $14.99 |
| Avatar: The Last Airbender Eternal | 9 | Mythic | $6.99 | $7.99Out of stock |
5 rulings from Wizards of the Coast
- 12 July 2019Agent of Treachery's effect lasts indefinitely. It doesn't wear off during the cleanup step, and it doesn't expire if Agent of Treachery leaves the battlefield. In a multiplayer game, it does expire if you leave the game.
- 12 July 2019If you gain control of a permanent "until end of turn," that effect will wear off during the cleanup step, after the end step. You'll control that permanent while considering Agent of Treachery's last ability.
- 12 July 2019If you don't control three permanents you don't own as your end step begins, Agent of Treachery's last ability doesn't trigger. If you no longer control three permanents you don't own as it resolves, you won't draw three cards. Those don't have to be the same three permanents each time.
- 12 July 2019Gaining control of a creature doesn't cause you to gain control of any Auras or Equipment attached to it. Gaining control of an Aura or Equipment doesn't change what it's currently attached to.
- 12 July 2019A token's owner is the player who created it.