Cheapest priced copy (Duel Decks: Merfolk vs. Goblins): $0.59 at Card Kingdom, near mint, their price list as of .
Goblin Diplomats 
Creature — Goblin · 2/1 · Rare · Magic 2014 · #141
{T}: Each creature attacks this turn if able.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.49 to $4.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Merfolk vs. Goblins | 42 | Rare | $0.59 | — |
| Magic 2014 | 141 | Rare | $0.59 | $0.49 |
| Magic 2014 Promos | 141★ | Rare | — | $4.49 |
3 rulings from Wizards of the Coast
- 1 July 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.
- 1 July 2013The controller of each creature still decides which player or planeswalker that creature attacks.
- 1 July 2013Creatures that enter the battlefield (or noncreature permanents that become creatures) after the ability resolves are affected by the ability and must attack if able.