u/Accomplished_Tax6431

This one is pretty simple. If you die with a sulfur cube bucket in your inventory, then at the site of death a sulfur cube will spawn with all your items floating around inside of it. You can then go to the cube, hit it with a sword to pop it, and your items will drop and you can collect them. This is useful for basically two scenarios

1. If you die in lava, the sulfur cube just floats on the lava with your items and you can then nudge it out of the lava to safe territory and pop it.

2. Your items won't despawn inside the sulfur cube and the cube itself wouldn't despawn either.

The non official name for these sulfur cubes that spawn with your dropped items is Sulfker Boxes but uhh I hope that holds up well in the translations for the game