Section 2: Spell Categories
Five main groups of spells, Tactical, Strategic, Domain, Global, and Champion. The first four are available to the Sovereign only, the last is available only to champions and is built from the first four.
1. Tactical Spells: These spells are your combat spells. Fireball, Ice Lance, Fear, whatever. These would represent your current run "tactical" spells. All of these would be available to champions, assuming they have the Essence to cast them. This would also include battlefield enchantments that last a certain number of turns.
2. Domain Spells: These spells are primarily enchantments which affect your domain (represented by the influence on the map). Some examples would be "Fire Ward" which would hit anything unfriendly in your domain for 1 fire damage per turn. Or Fountain of Life, which would increase the health regeneration of all friendly units in your influence. You could have spells that magical enhance your influence by a certain amount, or even change the terrain types (think "this spell changes every grassland in your domain into swamps"). These spells could be either single shot effects (heal everything in the domain 3 hit points) or turn spanning enchantments.
3. Global Spells: These spell affect the whole world. They are much more expensive than domain spells, but do similar things. Really nasty stuff like "reduces any unit with essence by 1, globally", or "slowly changes grassland to desert" or "randomly raises volcanoes outside your domain". Also, Disjunction (counter-magic) would go here, to counter said spells.
4. Strategic Spells: These spells basically are the ones that don't fit into the other categories. You'd have your unit enchantments, global map effects (direct damage to a unit stack), and environment altering (raise land, lower land, etc).
5. Champion Spells: This would be a subset of the four different types above. In order to make non-Soverign units more limited, you'd only put certain spells in here. Minor enchantments and tactical spells make the most sense.