Above the fatigue bar is the blue Magika bar that measures the amount of Magika you have. Magika, Mana, Spell Points ­ it’s all the same. This is the measure of how many spells you can cast, with spells of greater power costing more magika, and spells of lower power costing less. One of the biggest changes in game play in Oblivion from Morrowind is that magika now regenerates. I’d warrant a guess that Intelligence/Willpower will affect the regeneration rate, as it does the amount of magika you can have, but the regeneration rate was relatively slow on my non-magic using Wood Elf.