Let’s talk about why it’s important to have a PC change as the campaign happens. The idea of “My character wouldn’t do that” is, IMO, often built on the idea that the character will not learn or change or adjust based on the things they encounter in the world. So, let’s dig into this.
Inspiration from Blake Ryan. Blake poses the question, “have you ever used something from one game setting or system to another. For example using Githyanki/Githzeri/Mind Flayers in Conan or Lankmar? Something not part of the setting but not hard to insert either. Or, vampire clans from vampire the masquerade in D&D or Shadowrun? as pcs or npcs? Or, using Tyrannids in D&D.”
Side quests, how do they fit in to the grand scheme of the story, or does it? What if the party is sent on a side quest, but it doesn’t serve a purpose?