Oblivion:Resist Magic

With Resist Magic you have M% damage reduction from offensive spells. For example, if you have 50% Resist Magic with no other resistances and are hit by a spell dealing 30 points of magical damage, you only receive half the points of damage (15) instead of the full 30. Since nearly all poisons are also treated as Offensive Magic, Resist Magic also reduces the effects of those in the same way.
Notes
This effect can be gained for spell making via spells, choosing the Breton or Orc race, or the Aetherius Stone Doomstone.
This effect is disabled at the Enchanting Altar, but you can enchant an item with up to 20% magic resistance using a sigil stone.
In earlier versions of the game, there was a bug that caused some friendly spells to be resisted. This problem seems to have been fixed in one of the later patches.
A Breton already has 50% magic resistance. A Mundane Ring provides 50% magic resistance. So by simply wearing a Mundane Ring, a Breton easily achieves complete immunity to magic.
After 20 Fame is acquired, one can receive the Gates of Aetherius Greater Power by activating the Aetherius Stone, which provides 20% Resist Magic.
Other characters can obtain 100% magic resistance by combining some of the following items:
The Gray Aegis: 100% Resist Magic non-leveled shield found in the Arena; only obtainable through a glitch.
Mundane Ring: 50% Resist Magic; available in random loot starting at level 20, or from Raven Camoran's corpse if you are at least level 22.
Crown of Lindai: a leveled item that gives up to 35% Resist Magic (at level 25 or more); is acquired during Secrets of the Ayleids.
Morag Tong Cuirass: 25% Resist Magic light cuirass (Glass armor rating). This is a leveled item only found in the Mehrunes Razor plug-in, and its level is randomly determined (i.e. luck and/or reloading from saves is necessary to get the best one), starting at level 20.
'''Saviour's Hide: 25% Resist Magic'' light armor cuirass; obtained after level 17 through Hircine's Daedric Quest.
Diadem of Euphoria: a leveled light armor helm that gives up to 20% Resist Magic (at level 30 or more); worn by Thadon  . Also provides 40 pts of Fortify Magicka.
Transcendent Sigil Stones: 20% Resist Magic; can be used to enchant any piece of armor or clothing.
Black Band: a leveled item that gives up to 18% Resist Magic (at level 30 or more); acquired during A Watery Grave.
Ring of the Vipereye: a leveled item that gives up to 15% Resist Magic (at level 25 or more); acquired during Lifting the Vale.
Ring of Nihilism: 15% Resist Magic; available in random loot starting at level 9.
Spellturn Cloak from the Unearthing Mehrunes Razor plug-in can provide up to 15% Resist Magic, but only if you get it at level 20 or higher.
Ring of Mind Shielding  can provide up to 12% Resist Magic, but only if you get it at level 25 or higher. It is a reward for Everything In Its Place quest.

See also
Sections:
Resistances and Weaknesses: General information on how resistances and weaknesses interact.
Reflect vs. Absorb vs. Resist: Information on the similarities and differences between these effects. 

Related effects:
Weakness to Magic
Resist Disease, Resist Fire, Resist Frost, Resist Normal Weapons, Resist Paralysis, Resist Poison, Resist Shock 
Spell Absorption, Reflect Spell