Levels are a measure of strength for both MGs and anathema. MGs get levels by gaining experience. It is not known if anathema gain levels, or are simply created with the level they appear at.
Each level gives an MG ten stat points, to be distributed as they see fit.
"Levels ten, twenty-five, fifty, and 250 are considered minor milestones, while every hundredth level is a major one" Selene ch.27
MGs are assigned to tiers based on their level: 1-99 tier 1, 100-199 tier 2, 200-299 tier 3, etc.
Classes also have their own levels, although we know very little about how they gain levels. The only thing we know is that Cutie Pie's class, Pastry Princess, leveled up multiple times after the seed bearer was defeated. Her class was about ten levels lower than her level. (Ch. 25) A starting class gives on average one stat point per level, plus a one time start bonus (15 stat points in the case we know about).
A typical MG is somewhere between level 35-65 at the end of their first year, although a few will make it over level 100. (Mika, discord, 03/30/2024 4:00 PM)