The Elevation Pack is made of "Dwarvenite" and expands the Cavern Base Set. This pack was initially available as an Add-On pack to the Caverns Kickstarter. Set comes in both painted and unpainted versions.
The Elevation Pack comes complete with these 18 pieces:
(2) Elevated Bridge
(4) Elevated Curved Stair
(8) Elevated Large Pedestal
(4) Elevated Straight Stair