Cheapest priced copy (Modern Horizons 3): $0.99 at Card Kingdom, near mint, their price list as of .
Arna Kennerüd, Skycaptain 
Legendary Creature — Human Knight · 4/4 · Mythic · Modern Horizons 3 · #178
Flying, lifelink
Ward—Discard a card.
Whenever a modified creature you control attacks, double the number of each kind of counter on it. Then for each nontoken permanent attached to it, create a token that's a copy of that permanent attached to that creature.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $0.99 to $7.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Modern Horizons 3 | 178 | Mythic | $0.99 | $1.49 |
| Modern Horizons 3 | 371 | Mythic | $1.99 | $7.99 |
| Modern Horizons 3 | 485 | Mythic | — | — |
| Modern Horizons 3 Promos | 178s | Mythic | — | $4.99 |
5 rulings from Wizards of the Coast
- 7 June 2024To double the number of each kind of counter on a permanent, put another counter on it for each counter it already has. Effects that interact with counters being put onto permanents, such as the effect of Branching Evolution, apply as appropriate.
- 7 June 2024A creature that is equipped is considered modified no matter who controls the Equipment that's attached to it.
- 7 June 2024A creature with a counter on it is considered modified no matter what kind of counter it is or which player put it on that creature.
- 7 June 2024If, for any reason, an Aura token that would be created with Arna Kennerüd's last ability can't be attached to the appropriate creature, that token isn't created. If an Equipment token that can't be attached to the appropriate creature would be created, that token enters the battlefield unattached.
- 7 June 2024An Aura controlled by another player does not cause a creature you control to be modified.