The lava cube is a block either re-enacted to imitate the old beta texture of the lava or it was part of the unicorn garland update. The recipe is 20 Super Crate Box + Transmog Crystal + Lava in an oven or lab. It is farmable. It acts like a normal lava block,harming the user upon coming into contact with it.
When you make the lava cube, you only get one lava cube.
On item info it says DO NOT TOUCH
THIS ITEM CAN'T BE SPLICED