Spurious Sarcophagus
Source: Promotion. This item will be released as the uncommon loot from the WoW TCG Expansion "Tomb of the Forgotten".
The 
Spurious Sarcophagus is a toy obtained as an uncommon loot card from the World of Warcraft Trading Card Game expansion 'Tomb of the Forgotten', released on June 12th, 2012.
Guide awaiting review
Obtain the TCG Loot Card
Acquire the Spurious Sarcophagus loot card from packs of the WoW TCG 'Tomb of the Forgotten' expansion, or purchase the redeemed item from other players on the Auction House. It is the second of three loot items in the set, alongside the 
Sand Scarab and the 
White Riding Camel.
Redeem and Use the Toy
Once redeemed, activate the Spurious Sarcophagus to summon a sarcophagus that your character automatically enters, incapacitating you for up to 5 minutes while granting a buff described as 'It's hard to breathe and smells like mummies.' A sound effect plays for you and nearby players upon entering, and the toy has a 10-minute cooldown.
Tips
This toy is a convenient way to appear AFK during a break, but if another player initiates combat while you are inside the sarcophagus, you will be locked inside and cannot remove the buff by right-clicking it.
The Spurious Sarcophagus was also one of eleven possible rewards at the Blizzard Loot Elemental event at BlizzCon 2013.
