My favourite trait is, by far, Instructor.
It certainly isn't as powerful as choosing a divine patron at start and in some circumstances Archmage is clearly better, but I love the feeling of all my units upgrading faster.
I also quite like the imp advisor; it makes the early game somewhat more dynamic. Worth 5 picks in SP? Not
really, but hey, fun >> efficiency most of the time in SP.
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Re: divine patrons - I must second Agrela as a very
nice god to favour even if not the most powerful; You don't get the killer units or spells of e.g. Fervus or Lunord, but the good healing, population growth, and two very solid temple units (best healer in the Priestesses, very durable fighter in the Paladins) makes for a potent thematic combination for those who are natural turtle players.