I've been thinking this over for a while as an alternative to magicka tanking as it still doesn't make sense that a Destruction staff is a tanking weapon.
Now I know I'm not the most eloquent speaker nor the most knowledgeable person regarding balance for both PvE and PvP, but I tried to incorporate skills that'd be useful in situations for both.
I've tried to keep skills from being OP as possible and drawn all the skills from main Elder Scrolls games, at least in their basic forms.
Criticism is appreciated and expected, but all I ask is for constructive criticism instead of a "this is stupid" with no explanation as to why. Be brutal.


Ultimate: Light -- Create a blinding sphere of light, dealing x magic damage for y seconds. Allies can activate the Starlight synergy to also grant nearby allies Minor Evasion for z seconds.
Morph: Moonlight -- Restores x magicka over the duration to affected allies. Allies can activate the Moonlight synergy to restore y% of everyone's max magicka.
Morph: Sunlight -- Restores x stamina over the duration to affected allies. Allies can activate the Sunlight synergy to restore y% of everyone's max stamina.

Ability 1: Calm -- Calm an enemy target. If used on a basic enemy, it ends combat immediately and prevents them from aggro'ing for x seconds. Effect ends immediately if the target takes damage. If used on a boss or enemy player, it inflicts Minor Maim for y seconds.
Morph: Pacify -- Now works in a ground targeted AoE.
Morph: Apprehension -- Affected enemies will do x% less damage to you.
Ability 2: Fury -- Forces an enemy to attack you for x seconds.
Morph: Berserk -- Also reduces an enemies defenses, inflicting Minor Fracture and Breech for the duration.
Morph: Seething Fury -- Now deals x magic damage over the duration. y% chance to also enrage nearby enemies, taunting them to you. This can happen continuously.
Ability 3: Courage -- Empower your allies, granting them Minor Brutality and Sorcery for x seconds.
Morph: Fearless Leader -- Grants you x seconds of CC immunity.
Morph: Call to Arms -- Increases duration.
Ability 4: Fear -- Cause an enemy to be stunned by immense fear for x seconds.
Morph: Gripping Fear -- Also immobilizes enemies for x seconds after the fear ends.
Morph: Blinding Fear -- Affected enemies attacks have an x% chance miss for y seconds after the fear ends.
Ability 5: Silence -- Create an area of mind-numbing magic, prevent spells from being cast within for x seconds. Those that leave the area are silenced for y seconds afterwards.
Morph: Mage Bane -- Also deals x damage to the affected's magicka pool.
Morph: Atrophy -- Instead of a silence, now prevents stamina abilities from being cast and damages the affected's stamina pool.


Passive 1: Mind over Matter -- While an Illusion Staff is equipped, blocking costs magicka instead of stamina. Reduces the cost of Illusion Staff abilities by x% and reduces cost of block by y%.
Rank II: Reduces cost of block by x+% and reduces cost of block by y+%.
Passive 2: Menticide -- Increases the duration of Illusion Staff abilities by x% and increases the amount of damage you can block by y%.
Rank II: Increases the duration of Illusion Staff abilities by x+% and increases the amount of damage you can block by y+%.
Passive 3: Intelligent Armor -- While an illusion staff is equipped, every Illusion Staff ability slotted increases your Physical and Spell resistance by x and reduces the cost of block by y.
Rank II: While an illusion staff is equipped, every Illusion Staff ability slotted increases your Physical and Spell resistance by x+ and reduces the cost of block by y+.
Passive 4: Mental Energy -- Fully charged heavy attacks restore an addiional x% magicka.
Rank II: Fully charged heavy attacks restore an additional x+% magicka and y% stamina.
Passive 5: Hive Mind -- When an enemy is affected by an Illusion Staff ability, x% of the damage they deal to you is returned to all that are affected within 15 meters of you. Does not reflect killing damage.
Rank II: When an enemy is affected by an Illusion Staff ability, x+% of the damage they deal to you is returned to all that are affected within 15 meters of you. Does not reflect killing damage.


Regarding skills:
I know people will want to say Silence is OP, but, if it were implemented, it would have a cast time, so it can be interrupted, and a hefty cost.

Fear wouldn't make enemies run away, but would act as a stun, like Spindleclutch 1's final boss the Whisperer's fear.

Courage comes right from Skyrim, being a quick spell that boosts combat prowess. I looked over buffs and debuffs and noticed there aren't many sources of Minor Brutality and Sorcery.

Fury is a simple ranged taunt. Easier to unlock that Inner Fire, more reliable to use that a fully charged heavy attack from an ice staff. I, personally, do not like the idea of an AoE taunt, but included a pseudo form.

Hive Mind sounds like it would be very good, possibly even too good, but the return % would be low, no more than 15%, and even then, I think that's too high. Originally, I had wanted it to apply debuffs to all that are affected. E.g. if a templar used Power of the Light on one enemy that was affected by an Illusion staff ability, Power of the Light's Minor Fracture and Breech would be applies to all nearby enemies that are affected by an illusion staff ability.