Thank god someone said it. I wanted to reply but was a bit late to the party. Good thing you did.

I see also guides posted but I never read a single guide on strategies or tactics. I just... learned by myself.

You were that bothered with the fact I messed up the number of attacks and double strike? :-)

Yes :P

Okay, so you CAN assault a 4 hex city on a side such that not all garrison forces might be in the battle. Need to find a time where I can test this, to see what happens if the garrison units on the other side aren't involved (and thus killed) in the battle. Both of the 4 hex cities I have/will assault either didn't have units on far sides, or a hero was in the middle hex area (thus ending the side).

New questions:
1) Does that magic mace that increases my attack skill help archery as well, or just strike?

2) How is unrest controlled? Like, how do I determine how many/what kind of units will keep a population oppressed while I migrate it to something useful?

3) How is the chance of rebellion in any given turn calculated? I have a satry keeping an orc heavy calvary unit stable, and it takes a stack of 6 halfling level 1 units to keep a 4-hex level 2 city enslaved, while my hero or a halfling eagle rider will keep a level 1 unit enslaved.

4) Is the chance for unit rebellion calculated differently from city rebellion? If so, what formula is used for each one?

1) +attack from the mace is for melee only.

2) I usually experiment by moving units out one-by-one until the city says that it's in 'unrest' rather than 'enslavement'. I don't know what the difference between Enslaved and Oppressed is. Stronger units count for more as military police, and larger town require more.

I can't answer the other questions clearly, but with terrible morale or a city in unrest a rebellion/desertion will happen soon.

5) Is there a way to set "Display hex grid" to default to On? Having to hit F5 every time a map loads is kind of irksome.

6) What happens if you research all the spells currently available to you? Do you just get to set mana fully to production (as opposed to research)? I'm on the 3rd campaign map, and I'm currently researching the second to last spell in the research list

Yes. This means you can now afford a ton of buffing spells. (Haste for everyone!)

7) In a broad sense, is it generally better to dabble in several spheres of magic, or focus in a few?

Hmm for campaigns, I'd say focus, you'll have infinite time to research anyway. For multiplayer/scenario's I'd say spread out. The reason is that there are quite a lot of good tier 1 and 2 spells. TIer 4 have some really good spells as well, but it will take a long time to research and cast, but when you do... oh boy.

Still having a lot of diversity is also handy. In the end it's what you prefer.

I'd also Bless everyone. But preferably tier 2+ units.

The frogs... well, let's just say that one of the reasons you can beat Emperor AI despite their insane research/income/mana bonuses is that they mostly use it to summon frogs and such.

Still, armies of frogs are second only in awesomeness to armies of Dire Penguins.

I'd say it actually depends on the specific type of magic you're picking. Take spheres to get the spells you want.

Air magic? 1 sphere is enough. It gives you Haste and Chain Lightning. The later spheres can be useful, but don't add nearly as much bang for your buck.

Earth magic? All spheres are useful. 1 gives Stoneskin and Entangle, 2 gives Stoning, Gold Rush and Free Movement, 3 gives Lower Terrain and Enchanted Roads, 4 gives Raise Terrain. Death Magic? not very useful unless you have at least 2 spheres to get Terror, but better yet 3 to get Mind Decay.

Here's a list of all the spells per sphere in AoW, which is very helpful when deciding what to get.

In the campaigns, it's important to remember you'll eventually get a full 7 choices. In scenarios, you should decide what is most important to you and pick that. Or just go with default selections: often, if you play a leader that by default has sphere X, you'll start in a position with more nodes of that magic sphere, which can be very helpful.

Call hero is such a useful spell. It's easily one of my most favourite magics.

I'm not entirely sure, but I seem to recall it not working when playing the campaigns. I recall casting it a few times and getting some "no hero is available" message.

Is this right?

I believe it worked, but there's also a maximum allowed number of heroes in the campaign. I never tried to exceed that. At least I don't remember.

Edit: IIRC: it does work, but you can only a maximum amount of heroes to the next level

I'd been wondering what would keep me from sticking around an effectively beaten campaign map, leveling my hero to absurdity, and the answer is "map based level cap".

Found out what happens if you win a battle against a city, but the battle doesn't involve all units guarding that city: Southern is correct, in that the city becomes "contested", providing nothing to anyone. I realized an enemy hero was in one of the side hexes, so I took the extra turn to walk everyone to the other side and try it out.

Got my next two magic spheres, choosing air (haste) and water (water walk). I'll probably get two Life spheres when I get another choice.

So a magic oriented with a sphere of magic provides 10 mana per sphere of the aligned magic. Having 2 water spheres means each water node you control will give you 20 mana. This provides another reason to diversify one's magic spheres.
New question: Is there any reason NOT to raze any node that doesn't match one of my spheres of magic? For example, my 2 Life/2 Water/1 Air leader just took control of a Death node; why should I not burn it to the ground, since it doesn't do anything for me?

Might be worth keeping for vision; I'll have to check whether it see provides vision.