Within the mithril door is a large orb, and three hanging dragon heads. Each head can be lit by left-clicking, and once all three are lit they move forward and light the large orb. This then causes the Dragon Forge to activate, so the dragon platebody can be made there, providing the player has the ruined dragon armour lump, ruined dragon armour shard, ruined dragon armour slice and a blast fusion hammer on them, as well has having level 92 Smithing (or is being assisted by a player who has 92 Smithing).