Grampy_Bone
Arcane
There is a german-written strategy guide floating around somewhere 'FATE Kompendium' that explains it in further detail, but basically every character has four hidden class levels like Dungeon Master: Fighter/Ninja/Priest/Wizard. Certain actions in battle earns points for one of these classes, and when you go to that altar you'll level up in each class based on your accrued points. These levels provide bonus training points and extra stats.Should I come back later here to the shrine?
To gain points:
Fighter - Attack a lot.
Ninja - Shot/throw/steal/hide - Spend a turn in every battle having everyone hide to gain some easy free points in this
Priest - Status effect spells
Wizard - Direct damage spells and the 'grope' action
Other things may count towards these points but those are the easiest ones to use. Winwood can't use spells so Groping is the only way to get Wizard points for him. The class levels go up to 16 but become much harder to raise the higher they get, it's worth it getting most characters up to 4 in all classes because that means ~30 extra training sessions and a bunch of bonus stats.