How do shifters work?

[Uh... No thanks]

So the shifters are supposed to learn other skills but i dont get how exactly they work, do they learn then just for that one run? or permanantly? would they be able to learn every skill if its permanant?

[s_bautista098]

permanent you do have to level stones to fully use all the skills the class has and you can only level the class stone when the same class is in the same party as the shifter it levels based on the floors you get through

[Handoiron]

To give shifters other class skills you just have to put a shifter in your group and at least 1 of the class you're trying to learn. you get progress towards the stone for that class based on the number of fights they're in the group with the shifter. Having more than 1 of that class in the group will give that ammount of progress per fight (2 thiefs would give 2 "xp" to thief stone per fight). The progress towards learning is permanent so after you get progress you'll have that same progress for every shifter you hire.
To assign which classes you want your shifter to get skills from, you have to first have at least 1 fight with that class to make the stone accessable then hire a shifter, open party window and equip the class stone like an accessory in the far right 2 spot slot. You don't have to assign a specific class stone to learn that class. I recommend learning knight and probably thief first. once you learn the knight skills, replace knight with shifter and you get the 2nd class stone that you prefer.
Shifters have their own class relic that you'll most likely get in way late stage of the game and don't benefit from their assigned class' relics so you'll want to just stick them in the last party slot and forget they're there. This means you'll probably see the best results picking a second class that has a buff like thief (all treasures bonus item find), merchant (bonus gold find) or wizard (bonus warp progress).
At this stage in the game, you should be able to clear many thousands of levels per run so it shouldn't take too long to learn all the classes for your shifter even if you only put 1 of the learned class in group at a time. Typically you'd run with 3 of your preferred kill classes then learning class and shifter in last 2 slots where they'll slow your run the least, kinda like how you keep a knight at the back end of 3-4 DMs where he won't ever attack,