Cheapest priced copy (Kaldheim): $0.99 at Card Kingdom, near mint, their price list as of .
Kardur, Doomscourge 
Legendary Creature — Demon Berserker · 4/3 · Uncommon · Kaldheim · #324
When Kardur enters, until your next turn, creatures your opponents control attack each combat if able and attack a player other than you if able.
Whenever an attacking creature dies, each opponent loses 1 life and you gain 1 life.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $0.99 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duskmourn: House of Horror Commander | 223 | Uncommon | $1.49 | — |
| Kaldheim | 216 | Uncommon | $1.29 | $1.49 |
| Kaldheim | 324 | Uncommon | $0.99 | $1.99 |
| Starter Commander Decks | 5 | Mythic | — | — |
5 rulings from Wizards of the Coast
- 5 February 2021If a creature an opponent controls doesn't qualify for any of the above exceptions and can attack, it must attack a player other than you if able. If the creature can't attack any of those players, or if there are no such players, it must attack you or an opposing planeswalker.
- 5 February 2021Kardur's last ability will trigger no matter who controlled the attacking creature and no matter who it was attacking.
- 5 February 2021Kardur's first ability affects all creatures your opponents control, including any that enter the battlefield after the ability resolves.
- 5 February 2021If a creature affected by Kardur's ability could legally attack multiple players and/or planeswalkers, its controller chooses who it attacks.
- 5 February 2021If a creature an opponent controls can't attack for some reason (such as being tapped or having come under its controller's control that turn), then it doesn't attack. If there's a cost associated with having it attack, its controller isn't forced to pay that cost, so the creature doesn't have to attack in that case either.