Cheapest priced copy (Conspiracy: Take the Crown): $0.35 at Card Kingdom, near mint, their price list as of .
Shipwreck Singer 
Creature — Siren · 1/2 · Uncommon · Theros · #203
Flying
{1}{U}: Target creature an opponent controls attacks this turn if able.
{1}{B}, {T}: Attacking creatures get -1/-1 until end of turn.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Conspiracy: Take the Crown | 206 | Uncommon | $0.35 | $0.49 |
| The List | CN2-206 | Uncommon | $0.35 | — |
| Theros | 203 | Uncommon | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 15 September 2013If, during a player's declare attackers step, a creature is tapped, is affected by a spell or ability that says it can't attack, or hasn't been under that player's control continuously since the turn began (and doesn't have haste), 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.
- 15 September 2013The controller of each attacking creature still chooses which player or planeswalker that creature attacks.
- 15 September 2013The last ability affects creatures that are already attacking when it resolves. Activating it before combat won't affect any creatures that attack later that turn.