Wow... I had enough time to sleep, cut and dye my hair and nobody else posted in here yet. Cute. 
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If you do not have the Cloak of Non-Detection, you still can have temporary undispellable invisibility. Before engaging an enemy in combat, go to some empty room and cast Mislead. Leave the illusion in the room and now your Sorcerer is invisible until the illusion's duration runs out. True Sight will not dispel your invisibility because the enemy Mage/Cleric needs to have the illusion in their line of sight in order to dispel the illusion and your invisibility.