Other than the spells that come out of the magic research tree how does my sovereign gain new spells? How do I determine which spells my sovereign starts with ?
Your spellbook is determined by the ranks you have in the various schools of magic. For example if you know Death Magic III you will have access to Antipathy, Berserk, Blindness, Curse, Drain Life and Wither. Other than in the Magic tree there is no researching of spells, you get what you get and that's what you get. As you level up and gain more ranks in the various spell lines you will gain access to more spells.
The only way to gain new spell lines (ie you want Fire and did not start with it at all) is through the Steal Spirit spell. You sacrifice a champion and your sovereign steals one spell rank from the now deceased champion, as long as the rank you steal is greater than what you already have. Example you have Air II, Death II and Water II. If you sacrifice somebody with Fire II you will gain ONE (1) count it ONE (1) rank in Fire magic. Say you later on sacrifice somebody who has Air II, Earth II, and Fire II. You could choose to gain one rank in Earth (Earth I) or one rank in Fire (Fire II, since you already have Fire I).
Bonus note: The Wraiths faction has a special racial ability with Death Magic that unlocks a few extra spells. They're strong as hell and very useful, but only accessible to the Wraiths or if you made a custom faction.
Extra Bonus Note: Some spells require ranks in two schools to access. A great one which I really love is Sunder (Earth II, Fire II). It nukes a single elemental target for (4 x caster level) damage. It's not resistable, not typed so immunities to fire etc do not apply, and is great for killing elementals. There are a total of eleven (11) spells like this, you can look them up in the Hiergamenon for specifics but this is the list:
1. Tireless March (A/F). +1 movement for the stack, awesome!
2. Syphon STR (D/E). Steals strength and gives it to the caster. Kind of crappy IMO.
3. Sunder (E/F). Nukes elementals.
4. Stinking Mud (E/W). Awesome battlefield control, I've won a lot of battles with this spell.
5. Soul Burning (D/F). Expensive but huge single target nuke.
6. Nature's Call (E/L). Summons a bear to fight for you.
7. Horiffic Wail (D/W). Mass slow, not as good as it used to be but geez it's MASS SLOW.
8. Gentle Rain (A/W). +20% food for target city. Awesome.
9. Contagion (A/D). Poisons entire battlefield. Awesome if they are not immune to poison.
10. Calm (L/W). -10% unrest in target city. Awesome. I need to quit saying awesome but they are!
11. Battle Cry (A/L). Mass haste, a wonderful spell with lots of units.
Super Extra Bonus Note: Some quest lines grant spells. Alchemy and Confusion spring to mind, there are others as well.
- Manii Names