Cheapest priced copy (March of the Machine): $0.49 at Card Kingdom, near mint, their price list as of .
Doomskar Warrior 
Creature — Human Warrior · 4/3 · Rare · March of the Machine · #370
Backup 1
Trample
Whenever this creature deals combat damage to a player or battle, look at that many cards from the top of your library. You may reveal a creature or land card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $0.49 to $0.69 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| March of the Machine | 185 | Rare | $0.49 | $0.49 |
| March of the Machine | 370 | Rare | $0.49 | $0.49 |
| March of the Machine Promos | 185p | Rare | $0.49 | $0.49 |
| March of the Machine Promos | 185s | Rare | — | $0.69 |
6 rulings from Wizards of the Coast
- 14 April 2023If a permanent enters the battlefield as a copy of a card with a backup ability or a token is created that is a copy of that card, the order of the printed abilities is maintained.
- 14 April 2023If a backup ability targets the creature with backup, that creature will get +1/+1 counters, but it won’t gain additional abilities.
- 14 April 2023In some unusual situations (mostly involving damage redirection), Doomskar Warrior may deal combat damage to multiple players and/or battles at the same time. If this happens, its ability will trigger for each of those players and/or battles. Each ability will resolve separately, allowing you to look at a number of cards equal to the damage dealt to that specific player or battle.
- 14 April 2023The abilities that backup grants to the target creature are determined only once, at the time the ability triggers. They won’t change if the permanent with backup loses any abilities before the backup ability resolves.
- 14 April 2023If a backup ability causes another creature to gain abilities, the creature with backup will still have those abilities.
- 14 April 2023Backup confers only abilities that are actually printed below it. Any abilities that are gained by the permanent are ignored, including abilities gained due to a resolving spell or ability or copy effects.