What does Conduct Experiments (Shaper ability, requires Slave and a city) do? There's no 'pedia entry.
When Agents use their Shroud ability but don't leave the city until it wears off, they remain Hidden Nationality until they leave your cultural borders.
Possible I'm missing something, but Corgayle has both Channeling I and II and still can't learn any spells. Maybe because he's a Recon unit?
General tips: Do not rush Sluga. Build 2-4 Overseers ASAP, but use Familiars under them for development. When you get slaves from barbarians, turn them into Sluga and switch them out with the familiars. Sluga workrate is pretty much untouchable after a while - I believe two + Overseer can actually build two roads over flat terrain a turn - but they take a long time to build and you don't need that kind of workrate until you're expanding past your third city.
Don't start Recon until you're ready to go for Poisons. You can't get Subdue Animal, which is excruciatingly painful, and your Bounty Hunters are attack dogs rather then explorers - much better off using Adepts with Metamagic 1.
Best civic: Scholarship. Slaves are Specialists. I am strongly reconsidering my "Arcane past KOTE is optional" stance due to this. After burning through twenty slaves' worth of Khazad civilization with Corgayle and a Caretaker Matron (Corgayle had like -40% healing from a lair mutation, and Matrons are great for guarding between rounds) I was in love.
Look for cities that have good food resources and native commerce. If you let your neighbors grow for a while - you can actually just stomp with Corgayle, see below - you can farm them for slaves that will cover your production (and, in the lategame, research) needs quite adequately.
Consider your strategy when you pick your leader. Zaria picks up Agents alongside Corgayle, has a legitimate reason to go for Medicine (before which is Sanitation, a key component of useful cities), and has an extremely strong trait for you (your Overseers benefit from Charismatic way more then vanilla workers, and it's just as useful for your heroes and commanders as it is for everyone else's - also, mages). Mysticism, Crafting, KOTE, whatever resource techs you need, Poisons, Medicine is a good default path; once you get Corgayle, consider killing your nearest neighbors to get some breathing room until the lategame. Agents are hard to farm, but it's important to do so. Post-Medicine you can go for Slave Hunters, Adjuncts, or up the Arcane line as you choose, but nothing's in easy reach.
If you like challenges/masochism, Zaria is capable of an Altar victory if you pick up Philosophical and a religion. It's just not terribly functional (I like Order for her what with all the health I get access to from going Medicine, but that's after everything else) since nothing you want is on the religious path and you can get vampire candystripers anyway.
Jamal pairs the largely worthless Arcane trait with the very useful Philosophical trait; his strategy is identical to Zaria's except he pops Alteration with his second Sage and charges up the Arcane line. When you first get Karas and your worldspell, you can pop it (minimum of three Slave/Sluga to convert) and win right there. If you don't, you'll need to get access to metals for your Sluga and tons of mana for your Shapers. For the metals, you can cheat by using Dowsing + the absurd workrate of Sluga to get access just long enough for equipment promotions. Or, throw arcane techs at the AI for the metal line - be relatively sure you can get the arcane wonders first. You need one High Mage with Force III and Body III and as many Body nodes (+1 Force node) as you can get; I don't know if having these things improves your chances of GOOD mutation (IT SHOULD) but more effects is generally better, since you're already weighted for positive (so I hear). Now stack these things together - Karas + Behemoths + Mithril (Iron, more likely) + Aspect of the Berserker should be sufficient for whatever awaits you.
Mages are traditionally very hard to farm, and Corgayle doesn't make it easier (neither do Agents) since he kills the weaklings first. For this reason, and because it helps out Aspect of the Berserker anyway, consider going Force II - ranged attack XP is awful, but it's better then nothing and it's steady. In fact, if you're in no danger from a civ/barbarian city/goblin outpost, consider parking the mage and a defensive unit (like a GC with a fort) and just ranged attack/skip turn forever. A Great Commander with Arcane Student I & II is also nice. It's more of a concern for you then other civs since you want two spheres up to rank III very quickly, instead of being able to just cruise along with Spectres or Fireball.