Storm Fleet Negotiator

Mana cost: {2}{U}
Type: Creature — Siren Pirate
Power / toughness: 2 / 2
Set: The Lost Caverns of Ixalan Commander #78 (rare)
Price: $0.20 USD

Flying
Parley — Whenever this creature attacks, each player reveals the top card of their library. For each nonland card revealed this way, you create a Map token. Then each player draws a card. (A Map token is an artifact with "{1}, {T}, Sacrifice this token: Target creature you control explores. Activate only as a sorcery.")

Storm Fleet Negotiator has 2 printings, first in The Lost Caverns of Ixalan Commander (2023). EDHREC ranks it #9,456 among Commander cards. It appears most in Admiral Brass, Unsinkable decks (4,046 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 Storm Fleet Negotiator

Ahoy Mateys - The Lost Caverns of Ixalan Commander, led by Admiral Brass, Unsinkable

Commanders that run Storm Fleet Negotiator most

Deck counts from EDHREC.

Admiral Brass, Unsinkable: 4,046 decks
Admiral Beckett Brass: 690 decks
Nicanzil, Current Conductor: 480 decks
Captain Storm, Cosmium Raider: 378 decks
Ramirez DePietro, Pillager: 109 decks
Katara, Bending Prodigy: 56 decks
Zara, Renegade Recruiter: 50 decks
Maeve, Insidious Singer: 40 decks

Often played with Storm Fleet Negotiator

Cards that show up in the same decks on EDHREC.

Rulings

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 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: Except in some very unusual cases, the card each player reveals is the one they'll draw.
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: Map tokens are a kind of predefined token. Each one is a colorless artifact with the artifact subtype Map and the ability "{1}, {T}, Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery."
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: 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: 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.