I like it a lot! However (I am not experienced enough in anyway to judge if a class is broken) are the immunities that the Nihilist gains starting a bit low? it seems odd that one is gaining immunites to True Naming at 2nd level. But I a willing to admit ignorance.

An interesting idea: Would it be a good idea to make all divine classes (paladins' clerics, etc.) have a Nihlist as a Favoured enemy for free, since they are somewhat anti-divine?

I wonder if my DM would let me play this class?