Class Proficiency

Class Proficiency is a class improvement system introduced in Disgaea 5: Alliance of Vengeance.

Generic characters start at Proficiency Rank 1 of their class, slowly gaining Proficiency points to level it up as they kill enemies(amount gained depends solely on the enemy's level). As they rank up, they'll switch to the next tier of their class automatically(also unlocking that new tier for character creation) and unlock the Common Evility corresponding to that tier.

Note that while raising rank switches characters to a higher tier automatically, characters directly created at a tier higher than 1 will still start at Proficiency Rank 1.

Sub Class
Each unit can choose a Sub Class at the Assembly. While a character has one equipped they'll gain proficiency for that class instead of their ownoriginal one, allowing them to learn Evilities from other classes. Fully mastering a class also lets a character purchase that class' Unique Evility.

Every rank of Proficiency that a unit has earned raises their base stats permanently(with the higher ranks of each class giving a bigger amount), making Sub Classes important for maxing out a character's stats.

Note that Generic characters won't switch to a higher tier by improving a Class Proficiency different than their original. Unique characters don't have their own Class Proficiency, so they lose nothing by equipping a Sub Class.