Unlock at level 10.
Give access to some skills.
Most MG get 7 generic options to choose from. Though rarely extra Unique options will be given. “Achievements (as in what you achieve) determine what Classes you unlock, which also determine Skills.” Mikasane, Discord #mgg-genera 9/7/2023 11:17 PM
Mai managed to unlock 10 classes, although as of ch.37 we don't know what any of them are.
The only class we know any MG has is Cutie Pie's Pastry Princess, level 126. It is a pretty good assumption that this is not one of the starting seven.
“Unique Classes generally are stronger and offer earlier specialization which allows for earlier refinement.” Mikasane, Discord #mgg-general 9/7/2023 11:19 PM
On discord at 7/16/2024 11:20 PM, Mika gave an example of a beginner class:
[+10 Strength, +5 Vitality]
[+1 Strength every 2 Class levels.]
[+1 Vitality and Agility every 4 Class levels.]
[Strength aligned weapons are 5% more powerful.]
[Physical Based Magic and Skills are 5% more powerful]
[Unlocks unique REDACTED Skills.]
Thus picking this class instantly gives you 1.5 stat points worth of levels, as well as giving access to new skills and a small bonus to weapons, magic, and skills. Also, it gives, on average 1 stat point per class level. Assuming that classes level up at about the same rate as levels (which is the case for Cutie), that is an increase of 10% of stat growth.