Cheapest priced copy (March of the Machine): $2.79 at Card Kingdom, near mint, their price list as of .
Ghalta and Mavren 
Legendary Creature — Dinosaur Vampire · 12/12 · Rare · March of the Machine · #225
Trample
Whenever you attack, choose one —
• Create a tapped and attacking X/X green Dinosaur creature token with trample, where X is the greatest power among other attacking creatures.
• Create X 1/1 white Vampire creature tokens with lifelink, where X is the number of other attacking creatures.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
6 printings · $2.79 to $6.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| March of the Machine | 225 | Rare | $3.49 | $3.99 |
| March of the Machine | 307 | Rare | $2.79 | $3.49 |
| March of the Machine | 386 | Rare | — | $3.49 |
| The List | MOM-225 | Rare | $2.79 | — |
| March of the Machine Promos | 225p | Rare | $3.49 | $3.49 |
| March of the Machine Promos | 225s | Rare | — | $6.99 |
5 rulings from Wizards of the Coast
- 14 April 2023If you choose the second mode and there are no other attacking creatures, you won’t create any Vampire tokens.
- 14 April 2023Although the Dinosaur token enters the battlefield attacking, it was never declared as an attacking creature (for the purposes of abilities that trigger whenever a creature attacks, for example).
- 14 April 2023You choose which player, planeswalker, or battle the Dinosaur token is attacking. It doesn’t have to be the same player, planeswalker, or battle that Ghalta and Mavren is attacking.
- 14 April 2023If you choose the first mode and there are no other attacking creatures, you’ll create a 0/0 Dinosaur token. Unless something else is immediately raising its toughness, the token will die. You won’t have time to respond with a spell or ability to try and save it. A similar situation occurs if the greatest power among other attacking creatures is 0 or less.
- 14 April 2023For both modes, the value of X is determined as the ability resolves.