Fractals are used to unlock auto abilities on cards. Fractals can be farmed at Pleiades Lagoon when it is released on the 21 December. Different element fractals are farmed on different days. When you fuse a card with a fractal you get 1 of a select few random auto abilities unlocked depending on the element fractal used. You could also unlock a special auto ability which does not depend on the fractal used I'm a bit short on time so this is just a shortened version for now. I'll expand on it in the future.