The Iron Stairs is a stairs you can build (the Iron kit).
In-game description
Climbs one story, up through a gap left in the floor above. R turns it to climb north, east or west.SHOWN IN THE BUILD RING
Building it
It costs 2 
Stone, 1 
Iron Ingot, 2 Earth 1 Wind spirits. It needs 3 Jewels first. Take it down with DISMANTLE to get its cost back (see Building).
