Skyrim:Fortify Illusion

	Fortify Illusion
School	Restoration
Type	Defensive
Alchemy
ID	0003eb27
Base Cost	0.4
Base Mag	4
Base Dur	60
Enchanting
ID	0007a0fa
Base Cost	23
Items	Head, Neck, Chest, Finger
Availability (Click on any item for details)
Apparel Built-In Potions

Alchemy description: Illusion spells are <mag>% stronger for <dur> seconds.
Enchanting description: Illusion spells cost <mag>% less to cast.
Vampirism description: Illusion spells are 25% more powerful.

There are three distinct Fortify Illusion effects: one from Alchemy-created potions, one granted by enchanting armor, and one from vampirism. Their effects are as follows.

Alchemy

In potions, Fortify Illusion increases the magnitude of Illusion spells. This allows targeted Illusion spells to affect higher-level creatures, and is applied before perks. For example, a Fury spell cast with a Fortify Illusion +50% potion and the Rage perk will affect creatures up to level (6 * 1.5) + 12 = 21. Without the potion it would be 18, an increase of 3.

On the other hand, a Frenzy spell cast with the same potion but no perks will affect creatures up to level (14 * 1.5) = 21. Without the potion it would be 14, an increase of 7. Thus this bonus is best used on high-level spells and can be effective even if the user does not have Illusion perks.

The following alchemy ingredients can be used to create a potion of Fortify Illusion:

• Dragon's Tongue
• Dwarven Oil
• Mora Tapinella
• Scaly Pholiota
• Taproot

Enchanting

In enchantments, Fortify Illusion decreases the cost of Illusion spells, and the use cost of Illusion based enchantments.

The following items use this effect. You can learn how to enchant custom items with Fortify Illusion if you find one of the following items and disenchant it:

• All varieties of Armor, Helmets, and Robes of Illusion
  • Includes the enchantments of Minor Illusion, of Major Illusion, of Extreme Illusion, of Eminent Illusion, and of Peerless Illusion.

Artifacts and unique items that use the effect but cannot be disenchanted include:

• Archmage's Robes
• Diadem of the Savant
• Nightingale Hood
• Saarthal Amulet
• Vokun

Vampirism

Vampirism grants the Champion of the Night effect. This allows targeted Illusion spells to affect higher-level creatures but is applied after perks, making it very powerful for high-level Illusionists. For example, a Fury spell cast with Champion of the Night and the Rage perk will affect creatures up to level (6 + 12) * 1.25 = 22.5, rounded down to 22. Without vampirism it would be 18, an increase of 4.

On the other hand, a Frenzy spell cast with Champion of the Night but no perks will affect creatures up to level 14 * 1.25 = 18. Without vampirism it would be 14, an increase of 4. Thus, this bonus works best for characters who have invested in Illusion perks.

Keep in mind that dual casting an Illusion spell will double its strength—including any bonuses from Alchemy and/or vampirism—in exchange for almost tripling the cost.