The Creation sphere's god is not The One, but Amathaon. It isn't exactly creation, but birth or Fertility. Creation is the birth of new life, while Nature is change (the slow, predictable, cyclical process of growing up, not the chaotic change of the Fire Sphere. Both are opposed to the Stasis exemplified by Ice)
Force is mostly Balance. It seems less like a sphere unto itself as harmony and equilibrium between the other spheres. It does seem like it might be better represented not as magic but as more ordinary, Newtonian physics. I don't think that Gravity is related though. That seems more like part of the dimensional sphere, since General Relativity tells us it involves a bending of time-space. Of course, gravity would have to be rather different in Erebus, since that world is flat.
Raising or lowering Terrain would have to be an Earh spell, imho. Being a Cross-Sphere spell is also fine by me.
I would say that Force shouldn't be its own sphere, but Kyorlin did train Paimon as a master of Force/Balance magic.
I'm planning to implement all 21 spheres in the next version of my modmod. I've already finished Ice and Dimensional, although I may tweak them some.
Dimensional 1: Escape (just as it used to be)
-also grants the Duration1 promotion to summons. This (using xienwolf's modcomp) increases the summon's duration by 1, and also grants a little magic resistance and free xp, immunity to fear, immune to capture, no war weariness, etc. (The summoner Trait doesn't exist in my version, but starting with dimensional mana makes up for it in the case of the Sheaim and Infernals. Dimensional and Metamagic both require Arcane Lore.)
Dimensional 2: Open Gate - creates an temporary (requires-caster) Obsidian Gate in the city
-also grants the Duration2 promotion to summons. This (using xienwolf's modcomp) does everything duration 1 does, and gives +1 duration from combat victory.
Dimensional 3: Tesseract: summons a Tesseract unit. This is a non-combat summon that can carry cargo and perform Air Drops like BtS Paratroopers (bringing the cargo with it). This lets you transport an entire stack of units behind enemy lines.
-also grants the Planar Champion promotion to summons. This (using xienwolf's modcomp) increases the summon's duration by 1, and grants dimensional affinity and Blitz
Ice 1: Frost- temporarily turns terrain to tundra (or snow, if tundra already). It reverts back after x turn, where x equals a random number of turns from 0 to 30 multiplied by 1 more than the number of ice mana you have. There is also a small chance that Jungles/Ancient Forests/Forests/New Forests, or make them revert to a Forests/New Forests.
Ice 2: Summon Frost Giant- Summons a Frost giant, which is a strength 7 unit with ice affinity. It starts with Sentry1, Elemental, Vulnerable to Fire, and Immune to Cold, can get weapons promos, and is a melee unit permanent summon, so it can get other promotions. However, it can only be cast on Tundra or Ice, and cannot enter any other terrain, or feature
Ice 3: Blizzard - A direct damage spell, essentially Maelstrom but with Cold Damage. More importantly, it turns all nearby tiles temporarily to Snow and can destroy/downgrade Jungles/Ancient Forests/Forests/New Forests. This allows your Frost Giants to attack, and (since it even turns water tiles to snow) you can ignore your navy and march your armies straight across the frozen seas.
I'm still brain storming about creation. For now, I have moved Vitalize to Creation 2 (I made Nature 3 summon a random animal). I'm thinking one Creation spell will create a random resource on the tile (costing the promotion, taking several turns, and/or having a decent chance of failure). I'm also thinking one spell might boost a tile's yields directly (in python), rather than just changing the terrain. (This would have similar downsides, and might be good as another random result of the same spell.) A health-boosting/food-storing temporary building could also be good.
Creating Items seems more like an Enchantment spell to me. I was thinking I'd change Enchant Spellstaff to an Enchantment 2/Metamagic 2 cross-sphere spell, so that slot is open in my version. (Spellstaffs are also becoming equipment, so one unit can make the staffs for an army of casters.) Adding enough equipment for many uses of this spell seems like it could be tough though.
For force, I'd really like a spell that grants a temporary promotion that makes the unit ignore its actual combat odds, having a 50-50 shot in every battle, be it against an unpromoted goblin or the Avatar of Wrath. I have no idea how to do this though.
I was thinking that something to help the Grigori against both extreme religions would be good, so I was thinking that Force 1 could grant a promotion granting resistance to both Holy and Unholy Damage. When Kael removed Whirlwind from Air II he said he would move it to Force 2. I'll probably make the Force 2 spell be Repel, which would push enemies away (like whirlwind) and maybe also deals a tiny bit of Physical Damage (boosted by metamagic). For Force 3, I was thinking of using a Ring of Carcer-like mechanism to give the caster's tile a level requirement equal to the caster's level, but only while the caster remains there and (of course) it couldn't be allowed in cities.
