A mod that makes a chest with the same recipe as a normal chest, but with blocks of obsidian, and is unbreakable against explosions.
I think it is an exaggeration that IronChest needs to make a diamond chest to later make obsidian.
It could have the same space as a normal chest, and when standing next to another chest it becomes a big chest, with the space of the big chest.
Could you? I can help with the textures of the obsidian chest.
(To version 1.12.2)