Cheapest priced copy (Bloomburrow Commander): $0.49 at Card Kingdom, near mint, their price list as of .
Bident of Thassa 
Legendary Enchantment Artifact · Rare · Theros · #42
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.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
9 printings · $0.49 to $6.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Masters 25 | 42 | Rare | $0.79 | $6.99 |
| Bloomburrow Commander | 162 | Rare | $0.49 | — |
| The Brothers' War Commander | 80 | Rare | $0.99 | — |
| Commander 2015 | 86 | Rare | $0.79 | — |
| The Lost Caverns of Ixalan Commander | 146 | Rare | $0.49 | — |
| Modern Horizons 3 Commander | 177 | Rare | $0.49 | $3.99 |
| Theros Promos | 42★ | Rare | — | $2.79 |
| Starter Commander Decks | 44 | Rare | $0.49 | — |
| Theros | 42 | Rare | $0.69 | $4.99 |
2 rulings from Wizards of the Coast
- 16 March 2018If 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.
- 16 March 2018The controller of each attacking creature still chooses which player or planeswalker that creature attacks.