Levels of Eveything

N - Normal

M - Bronze

L - Iron

K - Silver

J - Gold

I - Platinum

H - Legend

G - Earth

F - Sky

E - Heaven

D - Holy

C - Mythical

B - Ethereal

A - Celestial

S - Sovereign

Z - Divine

Y - God

X - True God

So in cultivation of monsters and items (weapons, pills, et cetera)it is divided into three tiers: Low-tier, Mid-tier and High-tier.

Meanwhile in humans it is divided into five stars.