The Iron Door is a door you can build (the Iron kit).
In-game description
Steel-grey leaves strapped bright, in an ironclad frame. E opens and shuts it.SHOWN IN THE BUILD RING
Building it
It costs 2 
Iron Ingot, 1 
Wood, 1 Fire 1 Earth 1 Wind spirits. It needs 3 Jewels first. Take it down with DISMANTLE to get its cost back (see Building).
