The first class. Given when you first join the game or fuse

Gives x1 Power

The second class. Requires F class and 1 Million (M) power

Gives x2 Power

The third class. Requires E class and 50 Million (M) power

Gives x4 Power

The fourth class. Requires D class and 10 Billion (B) power

Gives x10 Power

The fifth class. Requires C class and 5 Trillion (T) power

Gives x35 Power

The sixth class. Requires B class and 1 Quadrillion (Qa) power

Gives x100 Power

The seventh class. Requires A class and 1 Quintillion (Qi) power

Gives x500 Power

The eighth class. Requires S class and 500 Sextillion (Sx) power

Gives x2.5K Power

The ninth class. Requires SS class and 400 Octillion (Oc) power

Gives x10K Power

The tenth class. Requires SSS class and 4 Decillion (Dc) power

Gives x100K Power

The eleventh class. Requires X class and 4 Undecillion (Ud) power

Gives x750K Power

The twelfth class. Requires previous classes and 3 Tredecillion (Td) power

Gives x9M Power (Fun Fact: I'm on this one!)

The last class. Requires previous classes and 3 Quindecillion (Qui) power

Gives x100M Power