Obsidian Chairs are usuable pieces of furniture that can be crafted in your Crafting Menu (opened by "Q" as the default key) or at any Crafting Table in older worlds.
The crafting-recipe for Obsidian Chairs will be unlocked by
- crafting (or taking) a Stone Chair, which is unlocked after crafting a Wood Chair
- creating Obsidian Slabs in a Processor from Obsidian Bars that are made in a Forge from Obsidian Ore that can be extracted from Nodes on the Fossil layer, in Caves, on Mountains or found in Iron Treasure Chests or obtained from Silver Keepas or Golden Keepas
- crafting an Obsidian Floor from Obsidian Slabs, Obsidian Rods and Melted Wax
To craft 1 Obsidian Chair, you'll need (as of R26 in December 2015):
- 1x Melted Wax made of Beeswax in a Forge or looted from Wood Treasure Chests or Stone Treasure Chests
- 4 Obsidian Rods made of Obsidian Bars in a Processor
- 2 Obsidian Slabs made of Obsidian Bars in a Processor
Crafting an Obsidian Chair is one of the unlocking requirements of the crafting recipe for Iron Chairs.
You can rotate Obsidian Chairs, however graphic glitches or displacements can happen when player characters sit down on or stand up from a chair that is placed sideways or upside down.
To make your player-character sit down, activate the chair by right-clicking or typing "f" (as the default key) while looking at it. Tables placed in front of the chair won't block this process, instead your player-character will sit down at the table.
Since R32 you don't need to equip any Power Cells to pick up any kind of crafted objects or blocks that have been placed into the world. Of course you won't be able to take these on claims of other players (or in worlds) where your permission level is set low.