Constellation Group: The Mage — The Elder Scrolls Online: Morrowind eGuide

The Apprentice raises Maximum Magicka and improves spellcasting:

Blessed: Increases your healing done by up to 15%.
Elemental Expert: Increases your Flame, Shock, and Magic Damage done by up to 15%.
Elfborn: Increases the damage and healing of your Critical Strikes with Magicka abilities by up to 25%.
Spell Erosion: Increases your Spell Penetration by up to 5280.

Minimum Rank	Name	Effect
The Apprentice Rank 10	Vengeance	When you block three spells within 10 seconds of each other, your next Magicka ability used within five seconds will always be a Critical Strike.
The Apprentice Rank 30	Spell Precision	Increases your Spell Critical by 12%.
The Apprentice Rank 75	Foresight	When you drink a potion, the cost of your next Magicka ability used within seven seconds is reduced by 80%.
The Apprentice Rank 120	Arcane Well	When you kill an enemy, you have a 20% chance to restore 1150 Magicka for up to three friendly targets within 2.5 meters of the enemy.

The Atronach raises Maximum Magicka and increases the damage done by basic attacks:

Master-at-Arms: Increases your damage done with direct-damage attacks by up to 25%.
Physical Weapon Expert: Increases your damage done with light and heavy attacks for Two-Handed, One Hand and Shield, Dual Wield, and bow weapons by up to 35%.
Shattering Blows: Increases your damage done to enemies with a damage shield by up to 25%.
Staff Expert: Increases your damage done with light and heavy attacks for destruction and restoration staves by up to 35%.

Minimum Rank	Name	Effect
The Atronach Rank 10	Retaliation	When you block a heavy attack, your next light attack used within seven seconds deals an additional 30% damage.
The Atronach Rank 30	Riposte	When you block an attack, you have a 15% chance to deal 2437 Physical Damage to the enemy. This effect can occur once every five seconds.
The Atronach Rank 75	Butcher	Increases your damage done with light and heavy attacks by 5% to enemies below 25% Health.
The Atronach Rank 120	Tactician	When you use dodge roll to dodge an attack, you set the enemy off-balance.

The Ritual raises Maximum Magicka while enhancing physical attacks and damage over time:

Mighty: Increases your Physical, Poison, and Disease Damage done by up to 15%.
Piercing: Increases your Physical Penetration by up to 5280.
Precise Strikes: Increases the damage and healing of your Critical Strikes with Stamina abilities by up to 25%.
Thaumaturge: Increases your damage done with damage-over-time effects by up to 25%.

Minimum Rank	Name	Effect
The Ritual Rank 10	Opportunist	When you interrupt an enemy, your next Physical Damage ability used within seven seconds deals an additional 15% damage.
The Ritual Rank 30	Perfect Strike	Increases your Weapon Critical by 12%.
The Ritual Rank 75	Exploiter	Increases your damage done against off-balance enemies by 10%.
The Ritual Rank 120	Last Stand	When you fall below 20% Health, you gain Major Heroism, granting 3 Ultimate every 1.5 seconds for eight seconds. This effect can occur once every 20 seconds.