Cheapest priced copy (Zendikar Rising): $3.99 at Card Kingdom, near mint, their price list as of .
Valakut Exploration 
Enchantment · Rare · Zendikar Rising · #303
Landfall — Whenever a land you control enters, exile the top card of your library. You may play that card for as long as it remains exiled.
At the beginning of your end step, if there are cards exiled with this enchantment, put them into their owner's graveyard, then this enchantment deals that much damage to each opponent.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $3.99 to $6.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Zendikar Rising Promos | 175p | Rare | $4.49 | $4.99 |
| Zendikar Rising Promos | 175s | Rare | — | $6.49 |
| Zendikar Rising | 175 | Rare | $4.49 | $3.99 |
| Zendikar Rising | 303 | Rare | $3.99 | $5.99 |
9 rulings from Wizards of the Coast
- 25 September 2020If you play a card this way, it leaves exile and becomes a new object. If it returns to exile later in the turn, you can't play it again.
- 25 September 2020You must follow the normal timing permissions and restrictions for the exiled card. If it's a land, you can't play it unless you have land plays available.
- 25 September 2020If you play the card in response to the end step triggered ability, that card won't be put into your graveyard and won't be counted when determining how much damage to deal.
- 25 September 2020In a Two-Headed Giant game, the end step triggered ability causes the opposing team to lose 2 life for each card put into its owner's graveyard.
- 25 September 2020You'll still pay all costs for a spell cast this way, including additional costs. You may also pay alternative costs if any are available.
- 25 September 2020If Valakut Exploration leaves the battlefield, any cards exiled with it remain exiled and can be played. The end step triggered ability won't trigger, and the cards won't be put into their owner's graveyard.
- 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.