Mana Regeneration
Mana Regeneration is to low at the moment 1/Turn for me. This is to low to make casters usefull, and furthermore makes the Tower of Magi (+2 reg) to strong. Mana regeneration should be in between 20% to 50% of your mana per turn.
Alternatively Shards could also add to mana regeneration per turn.
Spell Feedback
Combat Spells:
Protection from <Element> spells:
These spells should be permanent unit enchantments like protect unit (possibly castable in combat, too) because
you otherwise cannot use them to protect your units in the first turn, if the enemy acts first. So, in particular, you cannot protect your valuable champions against a strong caster, who might be able to kill them the first turn (considering the relation of damage done by spells (and weapons) compared to typical unit (and hero) Hitpoints this is and will be quite possible. Allowing these protections spells to be cast front up will help therefore to make them actually usefull. Considering a typical fight, instead of protecting a unit against some spell (in-combat) you will prefer to use your actions to cast some spells to kill that enemy caster and negate the threat in this way. This is even more true as in many cases you would need to cast protection agains several elements of magic.
Haste:
Haste should increase not only the max tactical movement (which is given to the unit the next combat turn), but also the actual tactical movement (so if a unit has a move of 0 it will have some movementpoints after beeing target of the spell and within the same turn). Typically you would cast this to move a unit fast to the front or backwards. However at the moment the effect take place with a delay of one turn, so its not quite so useful.
Arcane Arrow:
Being level 2 (I think) its only half as powerfull as Burn and Icebolt. As it costs 2 mana compared to 3 for Icelance ans also 2 for Burn, it should be even cheaper, (Burn dealing Int Dmg, but is only 1 Tile Range, Range not working atm). As it also consumes one action (which is also quite valuable) I would propose to reduce the mana cost down to 1 for Arcane Arrow, allowing it to be some kind of kill weak units spell for universal casters.
Fireball/Firebolt:
Similar to Arcane Arrow but even weaker (I think it does INT/3 Dmg, which is to low compared to melee weapons. It should be Int/2, that means if both spells are meant to single target as given by the spell description). As a result I would propose, to increase Dmg to Int/2 and reduce the Mana cost to 1 for Firebolt. Make Fireball some area Spell.
Drain Life:
should be Int/4 not Int/8. 2–3 HP Damage and healing for the typical caster are to low for 3 mana.
Also seemed not to work for me. A debuff text "Drain Life" appeared but the target lost no HP (Maybe because i was full HP at the time, but it should do damage nevertheless)
Lightning strike:
Only one tile, seems to work like the MoM Fireball did. This should be clarified a bit in the description, as it reads like Arcane Strike (which has a 3x3 tiles area of effect and deals damage once per tile, or so it seems) - ok its simply that squads are bugged and a 19 damage spell kills a whole squad of pioneers (why can one build a squad of pioneers??) which should have 5*10 Hitpoints. Lighnting strike should then have its damage adjustet to the value in the tooltip (Int/3) and also its area increased to 3x3.
Freeze Enemy:
Please add some indication which buffs/debuffs are active at an enemy/own unit. One can not see, which unit is affected by this (and other) spells.
Rock Slide:
No visible representation on the tactical map. Don't really know if it works, therefore.
Restoration:
Heal is too low. It should either cost less mana (2 or so instead of 4) or heal for more (Int instead of Int/2). It should be possible to negate a magic attack (if survived) with a magical heal. At the moment Restoration however is more expensive than the damaging spells while doing less.
Wall of Fire:
Can not cast this at all. Is this because of Range 0?
Higher Level Combat Spells
Note, that the following paragraph can be ignored, if the players souvereigns can choose top level weapons at the beginning, for cheap or free (like General Carrodus), as this would result in simply balancing for end game gear.
Considering the fact that melee has two ways to increase their damage (one powered by research, the other by increasing strength), I propose to add spells with higher int modifiers (while having similar cost) at higher spell levels. Therefore magicans will also have two ways to increase their damage (Arcane Research and Int). The final balancing should then depend on the weapon strength, typical Defense values and due to beeing limited per game-turn (Mana) balanced in a way that a caster does some more damage than a melee during similar times of the game. This might result in slightly reducing the int modifiers of the first level spells and adding several spells (might be Fireball Rank II) to the spellbook.
Overland Spells
Transfer Essence:
Please add some way to exactly select the target (champion) within the stack. This could also be usefull for the protection spells mentioned above, as well as further unit enchantments, which you might (should) include.
Reveal:
The revealed area could be one tile larger, I think, or, alternatively, could depend on the range of vision of the caster. It seems a bit overpriced and should be more in the line of 5 Mana. Furthermore you might allow to cast it on already unveiled territory to check for monsters or enemy armies.
Raise Land:
Should Raise flat land into a real hill. At the moment its more like a bunny hop. Also nothing appearing on the cloth map (not sure if hills should appear, through).
Greater Raise Land:
Built, in spite of the spells description, something i would call a hill and not a mountain . It looks like a Mountain on the cloth map however.
Create Desert:
Can't see any use for this, as landtye has no influence on economy and, as far as i noted, the desert has also no special influence on combat.
Summons
All Summons:
Summoned Creatures should not cost upkeep! They cost 0.2 at the moment. Confirmed for Familar, Imp, Stone Giant, Fire Giant. If you want to add upkeep in addition to the upkeep slots the upkeep should be payed in Crystals instead. The balancing of the units will be looked at i assume, and some special abilities will be added, so I will not comment on their strength - mostly.
Ok the fist thing is: Beiing able to summon only one unit of a type seems strange. This means, not the souvereign with the most essence can keep up the most summoned creatures, but the souvereign with the most spellbooks. It seems also natural, that you want to replace your weaker summons with stronger ones later on, which is not possible at the moment (due to to small number of available ones). Therefore you should remove the 1 per type cap on summondes units. However more powerfull units could require more upkeep slots. Doubling the upkeep slots would allow a finer tuning of unit upkeep.
A further improvement would be if you add some of the summons a second and third time to the spellbok as squads and so on. So level 1: Imp, (Upkeep 1) Level 4 Spell: Squad of Imps (Upkeep 2). This way the weak inital summons would reapear in the later game.
A second approach along this line, could be that some of the summons can be casted several times, adding a further creature to one unit. So first imp cast results in one imp (surprise surprise). Cast Imp again: You now have a unit constisting of two Imps and so forth. The number of creatures within a unit could capped by either spell level, Int or a fixed value. The required upkeep slots could also increase with more creatures per unit. Stonger creatures should however be one per unit and more of them should be allowed to exist (see above).
Familar:
The essence cost of the familar is a bit strange, because he additonally costs an enchantment slot. I would reduce the summoning cost to one or two essence and remove the upkeep slot. To make the familar, however, really usefull and uniqe his attributes should scale with the sumoners Int-attribute.
Wretched:
Absolutely underpowered 
Summon Daemon:
The Daemon should have some particle effects. And Maybe red instead of blue like on the Unit Card.
Minor Elementals/Elementals:
Those also should get some Particle effects.
Volcano, Flood and Earthquake:
Volcano:
Quite Impressive, should however be also visible on the cloth map (appears only after the magma dissaperared). Also lowering land on the side of a volcano should remove the magma as it looks quite stupid otherwise. I also noticed some bug that i could not "lower land" some tiles of a burned out volcano within one of my cities (Savegame, mountains next to Procipinee).
If can cast volcano on an enemy town, it is counter productive at the moment, as i can no longer attack the town for it being on a mountain ... and I can not lower the mountain as it is in enemy territory. The town should tehrefore be completely destroyed by the volcano and his lava (also for reasons of not contigous cities and generally stange behavious of "volcanoed" cities), or the volcano spell should be removed. I personally think destroying a city with one volcano is too overpowered, but it sure is fun, so keep it in. However it should be made sure that one can not beeline to game ending spells like this one. I further think that volcane needs some cooldown. Read my idea about shards below for an cooldown approach.
Flood and earthquake:
Similar to volcano. Seem rather too strong, but as volcano quite fun, so its ok for me. It ist, however, important to note that they can lead to cities getting fragmentet, or city buildings remaining while the city center is destroyed (see Screenshot, or the same Savegame as above for some half cities). So I again propose to completely destroy an targeted city. These spells should furthermore definitly gain some cooldowns (see shard idea below). Both spells should require two shards like volcano, I think. As a last comment to earthquake: make it not remove resources, remove the resource buildings, but not the resource itself ...
For all three spells make sure that the city enchantments, protecting agains magic work also as a protection agains these spells!!
Finally my newest idea about Shards!
This appeared to me while playing with the volcano spell, and also applies to the overpowered earthquake and flood spells. A simple way to keep shards spells really, really powerfull and nevertheless balanced, while also adding advantage to having more shards, would be to add a cooldown to each shard that is evoked by casting a corresponding shard-spell. So, e.g., you use your fire shard -> Its energy is depleted for 5 or 10 turns. The next spell using a fire shard can therefore only be cast after 5 or 10 turns. The length of the cooldown should be determined by the power of the shard-using-spell. If you have two fire shards, however, you can cast two really powerfull spells in succession. This would also allow keep these powerfull spells balanced, by long shard-cooldowns. E.g., the volcano, flood and earthquake spells should result in 10 to 30 turn shard-cooldowns, depending on the final pacing of the game. Weaker shard spells would result in 1 to 3 turns cooldown.
