Cheapest priced copy (Tarkir: Dragonstorm): $1.99 at Card Kingdom, near mint, their price list as of .
Dragonback Assault 
Enchantment · Mythic · Tarkir: Dragonstorm · #355
When this enchantment enters, it deals 3 damage to each creature and each planeswalker.
Landfall — Whenever a land you control enters, create a 4/4 red Dragon creature token with flying.
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
4 printings · $1.99 to $5.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Tarkir: Dragonstorm Promos | 179p | Mythic | $2.99 | $2.99 |
| Tarkir: Dragonstorm Promos | 179s | Mythic | — | $5.49 |
| Tarkir: Dragonstorm | 179 | Mythic | $1.99 | $2.49 |
| Tarkir: Dragonstorm | 355 | Mythic | $2.49 | $2.49 |
3 rulings from Wizards of the Coast
- 4 April 2025Whenever a land you control enters, each landfall ability of the permanents you control will trigger. You can put them on the stack in any order. The last ability you put on the stack will be the first one to resolve. (As a result, you can have those abilities resolve in the order of your choosing.)
- 4 April 2025A landfall ability triggers whenever a land you control enters for any reason. It triggers whenever you play a land, as well as whenever a spell or ability puts a land onto the battlefield under your control.
- 4 April 2025A landfall ability doesn’t trigger if a permanent already on the battlefield becomes a land.