Ok, I imagine new spells are not quite top priority, but since I went and typed this up I might as well post it.  At the very least, maybe some of these notions could make magic more fun.

This is a notion I had for a new book (and new school of magic).  If I had time I'd try to mod them in myself, but I don't (and it sounds like the mod tools aren't capable 
enough yet anyway).  So I'm releasing them into the wild instead.  If a modder picks them up, that would be awesome.

The numbers below are very, very, sloppy.  There's probably no point in trying to pick real, balanced numbers for this until we know what the new magic system and rebalanced game will look like.

Needs more variety at the higher levels (cool stuff to spend your shadows on).

OF THE BOOK OF SHADOW

The Book concerns the summoning and binding of Shadows.  Shadows are the native creatures of the Shadow Plane, an alien realm of existence devoid of light or magic.  They are  invisible, incorporeal, fearful of flame, and always hungry.  And what they are hungry for is the energy of life and magic.

Please note that shadows are not the undead.  Strange and terrifying as they are, shadows are as alive as any creature in our world, and while many are mere animals, the more  powerful ones have a will of their own.  It is even rumored that the higher inhabitants of the Shadow Plane have formed a complex hierarchical society, although to what end we  do not know.

Shadows do not come when they are called.  The only known way to summon a shadow is to open a door to the Shadow Plane and wait.  Many an aspiring Shadowmancer has met a  horrible fate at the tendrils of a Shadow which was too powerful for him to bind.  Be strong.  Be silent.  Be wary.

BASIC CONCEPTS

1. Shadows

A Shadow is a denizen of the Shadow Realm.  Shadows come in many sizes and shapes, but they all share a few distinctive attributes:

• All Shadows innately have a 50% reduction to physical damage received, and a 50% increase to fire damage received.
• Shadows cannot be identified on the strategic map, unless an enemy unit is immediately adjacent to their army.  Their presence is visible; however, the number and type(s) of Shadow contained in an army is hidden (except, again, by units adjacent to the army).
• Shadows can traverse any terrain at a cost of one movement point per square.
• Shadows deal "shadow damage", which is not affected by any damage resistence (if we ever see any, currently this doesn't seem to be in the game?).

Shadows come in the following basic categories:

• Lesser Shadows
• Shadows
• Greater Shadows
• Shadow Lords

The category should appear on the character card (where other characters have, e.g., "Soldier").

Shadows always appear "wild" (see below) and must be bound to your service by magical means.  Wild Shadows will attack any non-Shadow unit that comes nearby, razing any cities they happen to conquer; if enough Shadows are left alone in an area for long enough, they will start to band together and form armies.  Lesser Shadows and Shadows can be fully tamed, but Greater Shadows and Shadow Lords are merely compelled to serve you, and will eventually revert to being wild (and with a grudge against you for binding them!)

As you might guess, the earlier categories are both more numerous and less powerful.  In fact, Shadow Lords are unique creatures, and getting control of one is a huge benefit to your faction.

Many Shadow spells consume the essence of a bound Shadow, and become more powerful the more powerful the destroyed Shadow is.  Consuming the essence of a Shadow Lord can produce monumentally powerful effects ... if it doesn't realize what you are doing and consume YOU.

1.a.) Binding vs taming

A bound Shadow is coerced into your service.  It resents this fact, and after a certain amount of time will break free and attack any of your units and/or assets it can find.  
Shadows that have broken free cannot be bound or tamed by any faction for 10 turns, and cannot be bound or tamed by their former master for 20 turns.  Furthermore, sacrificing a bound Shadow is risky, as the Shadow might immediately break free in self-preservation.

Tame shadows, in contrast, will obey your every whim, and will happily allow themselves to be sacrificed for the greater good.

Shadows that are bound have a "loyalty level".  It starts at 100% and stays there for 5 turns.  Each turn thereafter, it decreases by an amount dependent on the strength of the Shadow.  If the Shadow fails a roll against its loyalty level, it will rebel and break free of your control.  Decreases in loyalty are as follows:

• Lesser Shadows: 1 per turn.
• Shadows: 2 per turn.
• Greater Shadows: 3 per turn.
• Shadow Lords: 4 per turn.

When you sacrifice a bound Shadow to cast a spell, you must make a Loyalty check at a penalty that is dependent on the Shadow type:

• Lesser Shadows: no penalty.
• Shadows: -5% penalty.
• Greater Shadows: -25% penalty.
• Shadow Lords: -50% penalty.

i.e., a Shadow Lord with 100% loyalty has a 50% chance of rebelling if you try to sacrifice it.  A Shadow Lord with 80% loyalty has a 70% chance of rebelling if you try to 
sacrifice it (effective loyalty is 80-50 = 30%).

2. Shadow Shards
A Shadow Shard an Elemental Shard that allows you to cast Shadow-aligned spells.  (technically, it is an *un*-shard, a hole in the universe through which the magic leaks out and shadows leak in, but we will leave that aside from the moment)  Shadow Shards do not occur naturally and must be created using the Desecrate spell.

A Shadow Shard spawns Shadows at the rate of a Small Shadow Gate (see below).

3. Shadow Gates

 
A Shadow Gate is a rip in the barriers between our world and the Plane of Shadow.  As long as a Gate is open, Shadows will pass through it on a continuous basis.  Shadow Gates can be "Small", "Medium", or "Large", indicating how large the tear in reality is.  Larger tear = more powerful shadows.

Every Shadow Gate will grow over time unless it is closed.  Shadow Gates are quest locations, with "Small" being quest level 2 and "Large" being quest level 4.  Any character with a high enough quest level can close a shadow gate by defeating a guardian army of Shadows (which becomes larger and includes more powerful shadows as the Gate grows).  

The progress towards the next level of Gate can be seen by any player who clicks on it.

Average rates of passage are given below in shadows-per-turn, as the parameter of a Poisson distribution.

• Small:  Lesser Shadows: 0.5 / turn; Shadows: 0.1 / turn; Greater Shadows: 0.01 / turn; Shadow Lords: 0.001 / turn
• Medium: Lesser Shadows: 2 / turn; Shadows: 0.5 / turn; Greater Shadows: 0.1 / turn; Shadow Lords: 0.005 / turn
• Large: Lesser Shadows: 6 / turn; Shadows: 2 / turn; Greater Shadows: 0.5 / turn; Shadow Lords: 0.01 / turn

Mechanically, a Gate starts with zero "size points" and gains one per turn.  Gates become Medium at 5 "size points" and Large at 20.  (thus, medium gates should be fairly common, but Large ones much less so)

Shadow Units
The number to the left of each unit is its relative probability of appearing.  When a new Shadow is spawned, its type is chosen randomly from the available Shadows of its 
level according to a weighted distribution.  So, for instance, a Shadow with weight 3 is always 3 times as likely to appear as a Shadow with weight 1.  (these weights are only relevant within a category; per-category probabilities are as given above)

Lesser Shadows:
  I'd like to have more variety here...

(4) Lesser Shadow: 3 HP, 1 AT, 0 DEF -- weak melee unit

      Ability: Shadow Bolt -- melee range attack, consumes 2x the AP of a normal melee attack but does not permit retaliation.

(1) Lesser Manaeater: 2 HP, 1 AT, 0 DEF -- weak mage-attacker

     Ability: Consume Mana -- leech one mana point from the target and gain life equal to the mana consumed.

  (the "manaeater" line needs a better name)

Shadows:

(4) Shadow: 5 HP, 2 AT, 1 DEF -- strong melee unit

      Ability: Shadow Bolt

(1) Manaeater: 3 HP, 1 AT, 0 DEF -- strong mage-attacker

      Ability: Consume Mana -- leeches 2 mana points

Greater Shadows:
 (4) Greater Shadow: 10 HP, 4 AT, 2 DEF -- powerful melee unit

     Ability: Shadow Bolt.

 (1) Greater Manaeater: 5 HP, 2 AT, 1 DEF -- powerful mage-attacker

    Ability: Consume Mana -- leeches 4 mana points

Shadow Lords:

Each Shadow Lord is unique (will occur at most once per game).

(5) Doloros, Shadow of Despair: 40 HP, 10 AT, 10 DEF

     Passive Ability: the enemy army's morale decreases by 5 per turn.

     Ability: Hopelessness -- decreases a single unit's morale by 20.

(5) Rastara, Shadow of Unreason: 40 HP, 10 AT, 10 DEF

     Passive Ability: enemy spellcasters have a 20% chance to fail their casts.

     Ability: Confusion -- target unit acts randomly for a turn.

(3) Mordath, Shadow of Hate: 50 HP, 12 AT, 12 DEF

     Passive Ability: each enemy unit within 2 squares takes 1 damage per turn.

     Ability: Mark of Hatred -- reduces target unit's DEF by 75% for two turns.

(3) Karstro, Shadow of Rage: 50 HP, 12 AT, 12 DEF

    Passive Ability: each other Shadow in the army gets a 100% bonus to AT.

    Ability: Blind Rage -- for two turns, target unit uncontrollably attacks the nearest enemy at a 50% penalty to AT, moving as necessary.

(1) Rexstra, Shadow of Hunger: 60 HP, 14 AT, 14 DEF

     Passive Ability: each other Shadow in the army gains one life for each damage dealt.

     Ability: Devour -- melee range ability, deals up to 20 damage to the target, gains one life per damage dealt.

(1) Azrael, Shadow of Death: 60 HP, 2 AT, 14 DEF

     Passive Ability: enemy army's max HP is reduced by 10%.

     Ability: Finger of Death -- kills a target unit outright. Can only be used once per battle; cannot target units with Essence.

     Ability: Cripple -- target unit's HP is reduced by 50% for three turns.

Shadow Spells

  Numbers here are pretty arbitrary and should be worked out better, particularly after we know more about what the magic system will look like.

Desecrate (strategic)
  Cost: 10 mana
  Requirements: 1 shard (any type)

  Converts a single shard of any type to a Shadow Shard.  You must control the target shard.

Bind Lesser Shadow (strategic)
  Cost: 5 mana
  Requirements: 1 Shadow Shard

  Compels a lesser Shadow into your service.

Shadow Gate (strategic)
  Cost: 10 mana
  Requirements: 1 Shadow, 1 Shadow Shard

  Open a small Shadow Gate on the target square.  The sacrificed Shadow becomes part of the quest army that must be defeated to close the gate.


Shadow Strike (enchantment)
  Cost: 5 mana, 1 Shadow
  Requirements: 1 Shadow Shard, 1 Enchantment Slot

  The target unit's attacks deal extra damage, which is treated as shadow damage, with the amount depending on the type of Shadow sacrificed:

  Lesser Shadow: 10% extra shadow damage
  Shadow: 25% extra shadow damage
  Greater Shadow: 50% extra shadow damage
  Shadow Lord: 200% extra shadow damage

Shadow Blast (tactical)
  Cost: 4 mana, 1 Shadow
  Requirements: 1 Shadow Shard

  Sacrifice a shadow to turn its essence into a blast of magical energy.

  Lesser Shadow: up to 3 damage
  Shadow: up to 6 damage
  Greater Shadow: up to 12 damage
  Shadow Lord: up to 40 damage

Shadow Ward (enchantment)
  Cost: 10 mana
  Requirements: 1 Enchantment Slot

  Shadow damage dealt to the target unit is reduced by 50%.

Consume Shadow (Strategic / Tactical)
  Cost: 1 Shadow
  Requirements: 2 Shadow Shards

  The caster gains mana equal to the current HP of the sacrificed shadow.
Tame Lesser Shadow (strategic)  Cost: 7 mana  Requirements: 2 Shadow Shards
  Tame a wild Lesser Shadow.

Bind Shadow (strategic)
  Cost: 7 mana
  Requirements: 2 Shadow Shards

  Compels a wild Shadow into your service.

Shadow Form (enchantment)
  Cost: 5 mana, 1 Shadow
  Requirements: 2 Shadow Shards, 1 Enchantment Slot

  The target unit shifts partly into the Shadow Plane and gains some of the innate bonuses of a Shadow, depending on the type of Shadow sacrificed:

  Lesser Shadow: 15% decrease to physicaldamage received and dealt, 15% increase to fire damage received, damage dealt is shadow damage.
  Shadow: 25% decrease to physical damage received and dealt, 25% increase to fire damage received, damage dealt is shadow damage, unit moves as a Shadow (1 movement point per square).
  Greater Shadow: 30% decrease to physical damage received and dealt, 30% increase to fire damage received, damage dealt is shadow damage, unit moves as a Shadow.
  Shadow Lord: 50% decrease to physical damage received and dealt, 50% increase to fire damage received, damage dealt is shadow damage, unit moves as a Shadow, unit is treated as a Shadow on the strategic map (cannot be identified).

Shadow Shift (tactical)
  Cost: 5 mana, 1 Shadow
  Requirements: 2 Shadow Shards

  The target unit is temporarily shifted very far into the Shadow Plane; physical damage dealt and received is decreased by 75%, and fire damage received is increased by 75%.

  Lesser Shadow: 1 tactical turn
  Shadow: 2 tactical turns
  Greater Shadow: 3 tactical turns
  Shadow Lord: 10 tactical turns

Rain of Corruption (tactical)
  Cost: 8 mana, 1 shadow
  Requirements: 1 Shadow Shard, 1 Fire Shard
  AOE: 1 square radius

  Balls of negative energy impact the target area, causing damage and decreasing DEF for two turns:

  Lesser Shadow: (up to) 2 damage, DEF-2
  Shadow: 4 damage, DEF-4
  Greater Shadow: 8 damage, DEF-8
  Shadow Lord: 25 damage, DEF-25

Poison the Well (enchantment)
  Cost: 10 mana, 1 Shadow
  Requirements: 1 Shadow Shard, 1 Water Shard

  Target city suffers an immediate population loss, and a penalty to future population growth (i.e., prestige) while the enchantment holds:

  Lesser Shadow: -10% population, -10% prestige
  Shadow: -20% population, -20% prestige
  Greater Shadow: -40% population, -40% prestige
  Shadow Lord: -75% population, -75% prestige

Blight (Enchantment)  Cost: 10 mana, 1 Shadow  Requirements: 1 Shadow Shard, 1 Earth Shard

  A slowly spreading blight is created, centered at the given location.  Within the blight, shadow units gain +25% to AT and DEF, and non-shadow units lose +25% to AT and DEF. 

 Cities lose 1 prestige per blighted square within their influence.

  The center of the blight is a quest location; a champion or sovereign can defeat a shadow army there to eliminate the blight.  (it should be possible to park an army on the center of the blight as extra defense)

  Lesser Shadow: blight radius increases by 0.1 squares per turn, quest is level 2, quest army is as for a Small gate
  Shadow: blight radius increases by 0.2 squares per turn, quest is level 3, quest army is as for a Medium gate
  Greater Shadow: blight radius increases by 1/3 squares per turn, quest is level 4, quest army is as for a Large gate
  Shadow Lord: blight radius increases by 1 per turn, quest is level 5, quest army is as for a Large gate *plus the sacrificed Shadow Lord*

Killing Winds (Tactical)
  Cost: 8 mana, 1 Shadow
  Requirements: 1 Shadow Shard, 1 Air Shard
  AOE: a "cone" leading away from the caster for 4 squares
  Duration: 3 tactical turns

  Shadow-tainted winds blow affected units back by 1 square and deal damage within the target area.  The winds continue for 3 turns, then disperse.

  Lesser Shadow: 3 damage per turn
  Shadow: 5 damage per turn
  Greater Shadow: 7 damage per turn
  Shadow Lord: 20 damage per turn


Shadow Deterrence (strategic)
  Cost: 10 mana, 1 Shadow
  Requirements: 2 Shadow Shards

  Shadows within the influence of the target city are less likely to attack your forces (but just as likely to attack anyone else's).

Mass Tame Lesser Shadow (strategic)
  Cost: 10 mana, 1 Shadow
  Requirements: 2 Shadow Shards
  AOE: as below

  Tame all lesser shadows in the area of effect, and form them into a single army (placed at the center of the effect).

  Lesser shadow: radius = 1 tile
  Shadow: radius = 2 tiles
  Greater Shadow: radius = 4 tiles
  Shadow Lord: radius = 100 tiles, but they do not form into a single army

Expand Gate (strategic)
  Cost: 10 mana, 1 Shadow
  Requirements: 2 Shadow Shards

  Add size points to a shadow gate.

  Lesser shadow: size += 2
  Shadow: size += 5
  Greater Shadow: size += 8
  Shadow Lord: size is set to maximum.

Tame Shadow (strategic)
  Cost: 10 mana
  Requirements: 3 Shadow Shards

  Tame a Shadow.

Bind Greater Shadow (strategic)
  Cost: 10 mana, 1 Shadow
  Requirement: 3 Shadow Shards

  Bind a Greater Shadow.

Hide Shadow (enchantment)
  Cost: 10 mana
  Requirement: 3 Shadow Shards

  Target shadow unit becomes invisible except to adjacent units.

Mass Tame Shadow (strategic)
  Cost: 10 mana, 1 Shadow
  Requirements: 4 Shadow Shards

  Tame all Shadows in the AOE (as Mass Tame Lesser Shadow).

Bind Shadow Lord (strategic)
  Cost: 10 mana, 1 shadow
  Requirements: 4 Shadow Shards

  Bind a Shadow Lord.  Failure chance determined by the sacrificed shadow.

Shadow Cleansing (strategic)
  Cost: 15 mana, 1 shadow
  Requirements: 4 Shadow Shards

  Banish all Shadows within the AOE to the Shadow Plane.  (AOE determined based on the sacrificed shadow)

Shadow Totem (enchantment)
  Cost: 15 mana
  Requirements: 5 Shadow Shards

  Targets a Shadow Gate or Shadow Shard; Lesser Shadows and Shadows spawned by the target are automatically tamed.  Greater Shadows and Shadow Lords remain wild.

Shadow Denial (enchantment)
  Cost: 20 mana
  Requirements: 5 Shadow Shards

  Target city cannot be attacked by Shadow units.

Weaken Reality (enchantment)
  Cost: 20 mana
  Requirements: 6 Shadow Shards

  The "now I win the game" spell for the Shadow line.

  Has the following effects:

• Shadow Gates gain 2 size points per turn instead of 1.
• Shadows pass through Shadow Gates at twice the normal rate.
• Each turn, a random Shadow gate opens somewhere on the map.
• Each turn, each existing Shadow Gate spawns new gates within 5 tiles of itself at the following average rate (Poisson distribution):
      + Small Gate: 0.05 / turn
      + Medium Gate: 0.1 / turn
      + Large Gate: 0.2 / turn
• The rate (above) at which new gates are created is multiplied by 2 for every 10 Shadow Gates that exist, capping at 1 new gate per existing gate.