Here is a video of the new spirit system in Cube World, currently in development by Wollay. You can upgrade you weapons not only with iron cubes (which increase the base damage) but also with spirit cubes. These cubes begin to glow when your spirit increases. When you perform a finishing move, their power is unleashed: fire spirit deals additional fire damage, unholy spirit drains life from the enemy and heals you by a small amount. Spirits will be very rare and most likely be dropped by bosses.
Check more Cube World videos here.