Cheapest priced copy (The Lost Caverns of Ixalan Commander): $3.99 at Card Kingdom, near mint, their price list as of .
Hakbal of the Surging Soul 
Legendary Creature — Merfolk Scout · 3/3 · Mythic · The Lost Caverns of Ixalan Commander · #29
At the beginning of combat on your turn, each Merfolk creature you control explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on the exploring creature, then put the card back or put it into your graveyard.)
Whenever Hakbal attacks, you may put a land card from your hand onto the battlefield. If you don't, draw a card.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
4 printings · $0.99 to $15.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Lost Caverns of Ixalan Commander | 3 | Mythic | $3.99 | $0.99 |
| The Lost Caverns of Ixalan Commander | 19 | Mythic | $3.99 | $15.99 |
| The Lost Caverns of Ixalan Commander | 29 | Mythic | $4.49 | $6.99 |
| The Lost Caverns of Ixalan Commander | 123 | Mythic | — | — |
8 rulings from Wizards of the Coast
- 10 November 2023If you control multiple Merfolk, you choose the order in which they explore. Make sure it's clear which Merfolk is exploring before you reveal any cards.
- 10 November 2023Once an ability that causes a creature to explore begins to resolve, no player may take any other actions until it's done. Notably, opponents can't try to remove the exploring creature after you reveal a nonland card but before it receives a counter.
- 10 November 2023If an ability instructs a creature to explore, its controller reveals the top card of their library. If it's a land card, they'll put it into their hand. Otherwise, they'll put a +1/+1 counter on that creature, then choose to either leave that card on top of their library or put it into their graveyard.
- 10 November 2023If no card is revealed, most likely because that player's library is empty, the exploring creature receives a +1/+1 counter.
- 10 November 2023In some unusual cases, noncreature permanents may explore. For example, if the creature card returned by Defossilize is somehow not a creature once it's on the battlefield, it can still explore. You'll take all the same actions, and you may end up putting a +1/+1 counter on the permanent. (Note that some effects target a creature, and those effects would still require a legal target to have it explore.)
- 10 November 2023Some spells or abilities might cause a creature to explore multiple times in a row. If you reveal a nonland card when a creature explores and leave it on top of your library, then the creature explores again immediately afterwards, you'll reveal the same card again.
- 10 November 2023If a resolving spell or ability instructs a specific creature to explore but that creature has left the battlefield, the creature still explores. If you reveal a nonland card this way, you won't put a +1/+1 counter on anything, but you may put the revealed card into your graveyard. Effects that trigger "whenever a creature explores" trigger as appropriate.
- 10 November 2023Each of your Merfolk creatures will explore during the resolution of Hakbal of the Surging Soul's first ability. Players won't be able to respond between the explores.