When your underground there's not many structures so I'm suggesting underground altars.
They would be made out of cobblestone and have a chest on them. The chest would have 0-5 iron 0-2 diamonds 0-1 of any enchantment books and 1-5 gold ingots. It would be as rare as a village.
They would be made out of cobblestone and have a chest on them. The chest would have 0-5 iron 0-2 diamonds 0-1 of any enchantment books and 1-5 gold ingots. It would be as rare as a village.
Very vague.