Just have a guy who's always right. Thats what I did.
I made a city ruled by a philosopher king who was beloved by his people, though he was a bit self-interested. He would constantly give the party really great advice that would benefit his standing one way or another.
When they wanted to free a city, he offered his army if they would install his nephew as the regent, and supplied them with a fool-proof battleplan.
When they came to him with advice on how to kill a monster, he ensured it was done beyond his borders so that its taint would not harm his people.
When a god died he advised the party to go to a lost city in the north and seek out an artifact he could use to learn more, however he also used that artifact for other purposes.