Cheapest priced copy (Foundations Commander): $1.99 at Card Kingdom, near mint, their price list as of .
Dragon Tempest 
Enchantment · Rare · Foundations Commander · #150
Whenever a creature you control with flying enters, it gains haste until end of turn.
Whenever a Dragon you control enters, it deals X damage to any target, where X is the number of Dragons you control.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
9 printings · $1.99 to $54.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2017 | 134 | Rare | $3.99 | — |
| Dragons of Tarkir | 136 | Rare | $3.49 | $14.99 |
| Foundations Commander | 150 | Rare | $1.99 | — |
| Game Night: Free-for-All | 74 | Uncommon | $3.49 | — |
| Iconic Masters | 125 | Uncommon | $2.99 | $12.99 |
| Dragons of Tarkir Promos | 136p | Rare | $8.99 | $34.99Out of stock |
| Year of the Dragon 2024 | 7 | Rare | — | $54.99Out of stock |
| Starter Commander Decks | 133 | Uncommon | $3.99 | — |
| Tarkir: Dragonstorm Commander | 94 | Uncommon | $2.99 | — |
3 rulings from Wizards of the Coast
- 17 November 2017The amount of damage dealt by the Dragon that entered the battlefield is based on the number of Dragons you control when the ability resolves.
- 17 November 2017If a Dragon entering the battlefield causes Dragon Tempest’s second ability to trigger but leaves the battlefield before that ability resolves, that Dragon still deals damage.
- 17 November 2017The two abilities aren’t mutually exclusive. If a Dragon with flying (which is most of them) enters the battlefield under your control, both abilities will trigger.