You hurl an undulating, warbling mass of chaotic energy at one creature in range. Make a ranged spell attack against the target. On a hit, the target takes 1d8. Roll another 1d8 to determine the damage type, do not add that 1d8 to the damage.

If you roll the same number on both d8s, the chaotic energy leaps from the target to a different creature of your choice within 10 feet of it. Make a new attack roll against the new target, and make a new damage roll, which could cause the chaotic energy to leap again.

At levels 5,11,17 you get an additional 1d8 of damage. So at 5 2d8, 11 3d8 and 17 4d8