Hakbal of the Surging Soul

Mana cost: {2}{G}{U}
Type: Legendary Creature — Merfolk Scout
Power / toughness: 3 / 3
Set: The Lost Caverns of Ixalan Commander #19 (mythic)
Price: $3.42 USD

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.

Hakbal of the Surging Soul has 4 printings, first in The Lost Caverns of Ixalan Commander (2023). EDHREC ranks it #3,944 among Commander cards. It appears most in Omo, Queen of Vesuva decks (6,687 on EDHREC). 1 public deck on TCG runs it. It has 8 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: not legal
pioneer: not legal
standard: not legal
brawl: not legal

Public decks that run Hakbal of the Surging Soul

Explorers of the Deep - The Lost Caverns of Ixalan Commander, led by Hakbal of the Surging Soul

Commanders that run Hakbal of the Surging Soul most

Deck counts from EDHREC.

Omo, Queen of Vesuva: 6,687 decks
Kumena, Tyrant of Orazca: 3,633 decks
Nicanzil, Current Conductor: 1,012 decks
Xolatoyac, the Smiling Flood: 289 decks
Thrasios, Triton Hero: 20 decks
Pavel Chekov, First Posting: 1 decks

Often played with Hakbal of the Surging Soul

Cards that show up in the same decks on EDHREC.

Rulings

2023-11-10: If 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.
2023-11-10: Once 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.
2023-11-10: If 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.
2023-11-10: If no card is revealed, most likely because that player's library is empty, the exploring creature receives a +1/+1 counter.
2023-11-10: In 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.)
2023-11-10: Some 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.
2023-11-10: If 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.
2023-11-10: Each 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.