The Obsidian Sanctuary is the sixth and the bottom floor of the Deep Caverns.
If you return upwards you will arrive at the Diamond Reserve.
The following items can be mined in this area:
They are Level 20 and have 300 HP. The Zombies and the Skeletons can be seen holding a Diamond Sword and Bow respectively and are wearing enchanted Diamond Armor and an Enchanted Diamond Block on its head.
The following items are drops from this area: