Spellbreak has six total classes so far incorporated into the game: Toxicologist, Conduit, Tempest, Pyromancer, Shoneshaper, and Frostborn.
Every time you finish a game as a certain class, you will gain experience and level up your class rank, not to be confused with your mage rank, which is a separate progression for your player character.
Leveling up your different class ranks can get you a plethora of unlockables. You can view this from the Mastery tab. The progression is full of badges, gold, talents, cards, cloudbursts, afterglows, and finally, a Triumph when you reach the max level.
The max level for class ranks is 20, but you can reach this goal six different times as each of the classes, meaning there is a total of 120 class ranks to level up if you want to max out everything.
If you are just looking to unlock all of the talents in the game (the only unlocks that affect abilities and gameplay), you will only need to level every class to rank 6.
Spellbreak is not only crossplay but also cross-progression; therefore, no matter which platform you are playing on, you can continue to level up your class rank.
Unlike the mage rank, it is less likely that we will see a cap increase for class ranks, especially if we get more gauntlets and classes to choose from in the future. That said, there is still a possibility of it.