The Bandos throne room sphere can only be bought from Oldak after the end of The Chosen Commander for 2 law runes and 1 molten glass. It is a stackable item. When broken, the sphere will teleport you to the Bandos's throne room seen during the quest. However, some of the monsters will now be attackable once their rock form is clicked on.
When the sphere first became available after the completion of the quest, anyone attempting to break the sphere would receive a message saying, "Nothing interesting happens." However, this was quickly corrected.