Blocks o' Bones are without a doubt one of the handiest blocks in the entirety of the Erebus mod.
Made as an elegant and flavourful solution to losing items on death, Block o' Bones holds on to your entire inventory at the time of death, and remains in the exact spot of your death until broken.
Once broken, a Block o' Bones will drop that entire inventory onto the ground for you to collect. You are also given a Block o' Bones Compass to find your last Block o' Bones (it acts like a predetermined Homing Beecon).
Block o' Bones can also spawn naturally in Antlion Overlord Pyramids, holding all sorts of Erebus dungeon-tier loot.
They cannot be collected in Survival, even with a Silk Touch tool. Any death with the Erebus mod installed will create a Block o' Bones, even those in other dimensions.