Cheapest priced copy (Battle for Zendikar): $0.49 at Card Kingdom, near mint, their price list as of .
Oran-Rief Hydra 
Creature — Hydra · 5/5 · Rare · Battle for Zendikar · #181
Trample
Landfall — Whenever a land you control enters, put a +1/+1 counter on this creature. If that land is a Forest, put two +1/+1 counters on this creature instead.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $0.49 to $2.29 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Battle for Zendikar | 181 | Rare | $0.49 | $1.49 |
| Duel Decks: Nissa vs. Ob Nixilis | 16 | Rare | $0.49 | — |
| Archenemy: Nicol Bolas | 69 | Rare | $0.69 | — |
| Battle for Zendikar Promos | 181 | Rare | — | $0.99 |
| Battle for Zendikar Promos | 181s | Rare | — | $2.29 |
3 rulings from Wizards of the Coast
- 8 November 2024Whenever 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.).
- 8 November 2024A 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.
- 8 November 2024A landfall ability doesn't trigger if a permanent already on the battlefield becomes a land.