Cheapest priced copy (Commander 2019): $1.29 at Card Kingdom, near mint, their price list as of .
Thieving Amalgam 
Creature — Ape Snake · 6/7 · Rare · Outlaws of Thunder Junction Commander · #150
At the beginning of each opponent's upkeep, you manifest the top card of that player's library. (Put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)
Whenever a creature you control but don't own dies, its owner loses 2 life and you gain 2 life.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $1.29 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2019 | 21 | Rare | $1.29 | — |
| Outlaws of Thunder Junction Commander | 150 | Rare | $1.29 | — |
5 rulings from Wizards of the Coast
- 23 August 2019Your opponents can't look at the card they own that you manifested.
- 23 August 2019If a creature you control but don't own dies at the same time that its owner leaves the game, Thieving Amalgam's last ability triggers. No player loses 2 life, but you gain 2 life.
- 23 August 2019In the Commander variant, you can produce mana that isn't of your commander's color identity if an effect lets you produce mana of that color or mana of any color, even though those symbols can't appear on cards in your deck. You may be able to turn a manifested creature card face up this way if it's not the same colors as your commander.
- 23 August 2019In a multiplayer game, if a player leaves the game, all cards that player owns leave as well. If you leave the game, the creatures you manifested with Thieving Amalgam's triggered ability are exiled.
- 23 August 2019If a creature you control but don't own dies at the same time that your life total becomes 0 or less, you lose the game before Thieving Amalgam's last ability can save you.