Each year you have a 75% chance of +1 exp in this trait (or at least that's how it should work). Alternatively, there is one decision related to owning the Temple of the Horned God (one of the places of power), which gives +10 exp to the demon. And that is all. Demons are designed more as opponents of the player, so their development is slow (but they are immortal, so theoretically they have plenty of time).

Thank you! So I guess I need to look for a place of power. So far I've been focused in artifacts in order to get the singularity...