Amorphous, Privilege and Scavenger, to put some examples. They're pretty OP once they get going, but you really need to invest a lot of effort at the start to make them work.
You can easily become an unkillable god with them, really. >>93939
I would say yes, because there's a lot of content locked behind soulstones, including amulets and contracts that let you play the game with something different than a Dragoon.
In other news, I started playing again, and boy oh boy, I wasn't expecting to get Amorphous ability from a tombstone.
If I don't get some reforge events for my HP amor soon, this run is as good as dead.