Bident of Thassa

Mana cost: {2}{U}{U}
Type: Legendary Enchantment Artifact
Set: Pioneer Masters #47 (rare)

Whenever a creature you control deals combat damage to a player, you may draw a card.
{1}{U}, {T}: Creatures your opponents control attack this turn if able.

Bident of Thassa has 11 printings, first in Theros (2013). EDHREC ranks it #446 among Commander cards. It appears most in Alela, Artful Provocateur decks (9,394 on EDHREC). 7 public decks on TCG run it. It has 2 official rulings.

Legality

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

Public decks that run Bident of Thassa

Ahoy Mateys - The Lost Caverns of Ixalan Commander, led by Admiral Brass, Unsinkable
Bangarang!, led by Derevi, Empyrial Tactician
Creative Energy - Modern Horizons 3 Commander, led by Satya, Aetherflux Genius
Family Matters - Bloomburrow Commander, led by Zinnia, Valley's Voice
First Flight - Starter Commander Decks, led by Isperia, Supreme Judge
Swell the Host - Commander 2015, led by Ezuri, Claw of Progress
Urza's Iron Alliance - The Brothers' War Commander, led by Urza, Chief Artificer

Commanders that run Bident of Thassa most

Deck counts from EDHREC.

Often played with Bident of Thassa

Cards that show up in the same decks on EDHREC.

Rulings

2018-03-16: If a creature can't attack for any reason (such as being tapped or having come under that player's control that turn), then it doesn't attack. If there's a cost associated with having a creature attack, the player isn't forced to pay that cost, so it doesn't have to attack in that case either.
2018-03-16: The controller of each attacking creature still chooses which player or planeswalker that creature attacks.