I love the direction this is going and I love the models, but I don't like the overall feel. From a story-line standpoint, this sort-of paints magic as being "bad" and tech being "good". None the less, I think the basic idea of the necro and monk are very good. Thus, I have something to offer
The magic faction can call these the "Path of Corruption" and "Path of Nature" and the tech faction can call them the "Path of Enlightenment" and "Path of Reason." I've only filled out this concept completely for the Path of Corruption, the rest are at varying stages of incomplete. I realize that by introducing more possibilities, it's almost like having 4 different factions and they all have to balance in the end while maintaining their uniqueness.
Magic Faction: Path of CorruptionWhile I think we should leave the Demon (50g unit) as is, we should maybe associate Hell Gate (and daemon giant) with Path of Corruption and use Treant on the Path of Nature.
Building: Necromancer Tower - requires Library and Ancient Summoning?
+ create Necromancer or morph from either Initiate or Summoner.
+ research: Summon Undead Behemoths
+ research: global enhancement (workers move faster and carry more because of fear?)
+ research: Lich - very slow upgrade and requires archmage tower, maybe dragon call and necro extension building (below)
Building: some necro extension (graveyard? crypt? morgue?) - requires Necromancer Tower
+ research: Lich attack B (see Lich unit below)
+ research: Lich can move slowly while controlling enemies instead of being immobile?
+ research: improve some other Lich ability
Unit: Necromancer - pretty much as previously described
+ Summon Undead Infantry
+ Summon Undead Behemoths (researchable)
+ some ability to heal their skeletons & zombies (researchable)
+ Morph into Lich (researchable)
Unit: Lich - Lich looses summon abilities, moves slower than necro, has a little lower HPs and (no?) armor, but may possess some other defensive properties like a researchable damage shield or deceptive defense like an illusionary "shadow" of the Lich that follows him around and fools attackers into attacking it instead of the real Lich. When such a "shadow" is close to the Lich, spell effects from the Lich's casting will only appear from one or the other, randomly alternating.
+ magical attack A: For a name, I was thinking "Decay", "Venom", some kind of fire that keeps burning. - initial damage plus damage over time, 4-ish splash radius, moderate EP cost, slow recast rate. Possibly a researchable effect that decreases some stat of opponent.
+ magical attack B (researchable): "Enveloping Despair", "Leech" or something - damages opponent and lowers a stat temporarily while transforming some of the damage into health for the Lich. higher EP cost.
+ "Control" or "Dominate" (innate): Can control up to 3 enemy units. Monks and all "holy warriors" should be immune to this effect (but not scientists). Controlled units will suffer constant health drain from the effect, but will be able to siphon *some* of the life from their opponents in battle (a small percentage). Can control up to 3 units at once and cannot attack while controlling other units. For balancing, may make him immobile or move slower while controlling if needed. The Lich's EP should also suffer while controlling units, relative to the number of units controlled. Perhaps 1 unit causes slow regen, 2 units no EP regen and 3 units causes EP drain. Running out of EP while controlling 3 units will cause one of the slaves to be released.
Unit: Undead Infantry -- pretty much as described
+ submerge/bury: as described or where the ability is free and unlimited but they are immobile and cannot attack but ambush the enemy if the enemy comes near or have some limited (researchable?) attack while submerged.
Unit: Undead Behemoth -- pretty much as described
Magic Faction: Path of NatureInitiates gain ritual to summon a treant from a tree. I'm not certain how to work the costs on this one or rather or not it should use up the tree, but I'm thinking it should just use wood and leave the tree.
Building: Grove - requires library and manna compression (or something else like that). Can only be built on existing trees or must have at least one or two trees in the place where it's built. Workers can damage the building by harvesting wood from it, so be careful. This building regenerates.
+ create Druid or morph from Initiate.
+ research: "Gift of Nature" - all organic units (humans, drake rider, etc.) gain regeneration and maybe gain the ability to travel more quickly through forests. This might be tricky to implement without just letting them walk straight through trees (which is a possibility). The later might also be a separate upgrade.
Building Change: Mage Tower+ upgrade to "Blessed Mage Tower" or "Entwined Mage Tower" - requires Grove
Building: Entwined Mage Tower - appearance changes so that vines cover the building and it should get some shrubbery or something.
+ research: "growth"-ish name - a small amount of wood is automatically added to supply every few seconds.
Unit: Druid+ Healing Ceremony: Heal a friendly non-demon unit as well surrounding units, but at a slower rate than the target.
+ Can travel across treetops and is an air target when above trees? (researchable)
+ Summon Sprite/Pixie?
Unit: Treant - Replacement for Daemon Giant on Path of Nature summoned by Initiates from forest. Is an expensive, slow moving, heavy warrior unit with regeneration.
+ ability: Take Root (researchable) - while rooted, the treant appears to be a normal tree, but can attack enemies that come near it and gains regeneration and armor. Rooting and unrooting should not be instant.
Unit: Pixie/Sprite? - I was thinking some type of very delicate, fast moving helper unit that brings enhancements (but not healing) to friendly units when near. Maybe Druids obtain these and they fly around and visit friendlies within a mid to large-sized radius giving them some enhancement.
Technology Faction: Path of EnlightenmentI was thinking that this would be mostly as originally described except that "holy" units shouldn't be as powerful. Rather, I think they should just gain defensive improvements, prayer and maybe some other researchable blessing.
Building: Abby - Requires Barracks & Farm (something like that). Any holy fighting units should require "Training Field" from Barracks as well.
+ create Monk
+ research: global enhancement (bonus to armor and health as an upgrade instead of blessing?)
Unit: Monk+ Heal friendly organic units.
+ Ability to repel undead units and perhaps free units from Lich control.
Technology Faction: Path of ReasonI don't have this one well thought yet, but the science route brings fewer new units and more enhancements to existing units through advanced technology.
Building: University - requires Blacksmith & Technodome.
+ create some unit? maybe a physician?
+ research: advanced tools - workers and engineers build and harvest faster. Engineers may get some other benefit from this
+ research: poison arrows - limited (maybe each archer gets 3 of them), will do damage over time to target.
+ research: compound bows - increases range and damage
+ research: aerial units move faster
Building: Academy or War Office - requires University and maybe Advanced Tools.
+ research: advanced offensive warfare - lowers the number of kills required for a unit to advance.
+ research: advanced defensive warfare - castle drops burning oil or rocks on non-ranged attackers? Defensive Towers do more damage?
+ research: maybe catapults are upgraded to cannons? Does that break the era this game is set in?
I hope I'm not going off the deep end here, but you may have started something really cool.
Edit: Added more stuff