When you enter the room of Vaeleztras the Corupt, there are many Goblin-Dudes inside which you have to kill. Pull them all, except Goblin-Spellbinders ! Leave them out of combat. Kill the other Goblins and loot them. After that, all must leave BWL, except of one. He stays inside and let himself get killed from the Goblin Spellbinder which he aggro. When hie dies, the Goblins are ALL reseted. You can enter BWL again, and blow them down and loot the Elementium when u r lucky.