Cheapest priced copy (Foundations Commander): $0.49 at Card Kingdom, near mint, their price list as of .
Terror of Mount Velus 
Creature — Dragon · 5/5 · Rare · Foundations · #764
Flying
Double strike (This creature deals both first-strike and regular combat damage.)
When this creature enters, creatures you control gain double strike until end of turn.
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
5 printings · $0.49 to $2.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Forgotten Realms Commander | 145 | Rare | $1.99 | — |
| Foundations Commander | 179 | Rare | $0.49 | — |
| Foundations | 549 | Rare | $2.79 | — |
| Foundations | 764 | Rare | — | — |
| Theros Beyond Death | 295 | Rare | $2.29 | — |
2 rulings from Wizards of the Coast
- 24 January 2020Multiple instances of double strike on the same creature are redundant.
- 24 January 2020The triggered ability affects only creatures you control at the time it resolves. Creatures you begin to control later in the turn won't gain double strike.