Gateway Control Stone

Gateway Control Stone allows a player to be automatically transported when they walk near a Demonic Gateway created by a warlock in the party or raid.

Source
This item can be purchased by only a handful of reagent vendors in the major cities for :
 * in Stormwind City
 * in Siege of Orgrimmar
 * in Stormwind City
 * in Stormwind City
 * in Orgrimmar