I love Arcos!!!

[Taqwus]

Skeptic prophets can be entertaining, at least if you have a twisted sense of humor. Theoretically, a Skeptic prophet with a Stone Idol, preaching, should have rather interesting effects inside hostile dominion. Unfortunately, they're not very stealthy (+0 ?), and are likely to die easily once caught unless you keep them in border regions only and have 'em set to retreat.

Regarding nation choices, you may want to be careful in games with few players, as some match-ups may be more unbalanced than others. Man versus Carrion Woods Pangaea on a fairly small map, for instance, might be somewhat ugly given that a longbowmen is one of the better basic units for countering CW base undead -- the latter don't have shields or armor, so die easily under massed arrow fire. C'tis Miasma dominion has a nasty diseasing effect, good for defense... but not against undead armies. And so forth. Some will have an easier time than others.