Okay, so I'm immortal, part of small elite group of immortals, and we are all basically "good" - let's say it's unlikely to hide being evil for millennia.  What could drive me to disrupt status quo?

1.  Boredom:
What if I've reached a level of boredom that prompts me to do something to cause a new reaction?  This would be some kind of developed sociopathy.

2.  Loss:
Perhaps I've lost someone close to me through accident.  No murders, yes, but perhaps through "normal" attrition, like a wreck.  Now I can't handle the pain, or I want to change things so that the accident doesn't happen again, or I want to punish someone responsible.

3.  Outside influence:
We've been a static society for millennia.  Now we've encountered humans.  Humans flit through life, and make us realize that life is precious, meant to be finite if we want to appreciate it.  The fear of death gives humans a drive and ambition that we have lost.  Or maybe instead, they are encroaching on our way of life, and we need to beat them back or lose what we are - though that very action may mean losing who we are anyway.

4.  Crisis:  Superman's Kryton had a nice utopic society, but it prevented them seeing the truth of their eminent destruction, and those that argued for change were naysayed.  That caused Zod to act outside of the norm.  

Finally, you might watch Star Trek The Next Generation, particularly the episodes involving Q.  Q is "all powerful", bored, and outside of the norm of his populace.