Magicka is the character resource that is used to fuel spells in The Elder Scrolls II: Daggerfall. This is represented by the blue status bar, and measured in spell points. Every spell has an associated magicka cost, and the current spell point total must exceed that cost in order to cast it. Once cast, magicka is drained by this amount. Aside from the inability to cast spells, there is no penalty if magicka falls to zero.
Maximum spell point total is 0.5x of the Intelligence attribute, although a class with an Increased Magery special advantage can potentially exceed this. All spells require at least a minimum of 5 spell points.