So I've seen my fair share of wild surges in my game by now. It leaves me wondering how the surge is computed. Does caster level apply to all surges, both from Nahal's and the 5% per cast chance? If so is it base caster level or the modified caster level from the random level adjustment? I'm just wondering if I should be running around with Chaos Shield up during battles in case of a wild surge (not from Nahal's).

Chaos Shield's bonus does add for all kind of wild surges. When you cast Nahal, you also get your actual wild mage level as a bonus too, which stacks with chaos shield. So a lvl 40 wild mage with chaos shield active will have a very good chance of casting any spell with Nahal's Reckless Dweomer. (so what I am saying is, Nahal's wild surges are almost always better than regular, 5% chance wild surges, since you do not get your level bonus in the latter.)

Thank you for answering my question succinctly and clearly. I'm semi-regretting going Cleric/Wild Mage instead of vanilla Wild Mage since I don't get as high of a bonus to my Nahal's.

Can anyone tell me if the caster level bonus to Nahal's Reckless Dweomer is strictly the level of the character or if the +/- random level adjustment for being a Wild Mage applies?

Strictly caster's bonus level IIRC, and the same holds true for determining what type of surge effect you'll get. The random level adjustment only affects the spells themselves.

I'm both relieved and simultaneously disappointed. It's good to know my high level Wild Mage will have fairly reliable wild surges. But at the same time it seems to trivialize the +/- effect on caster level.

Early in the game the +/- effects are tremendously important. When you're level 9 and you get a -5 to your spell power, that is a HUGE disadvantage. It's not so much an issue when you get above level 20, but until then it can turn the tide of the battle in unexpected ways, especially if you rely on magic a lot (which I do when I play a Wild Mage).