I don't understant, how "magic power aviable" works. For example, I find item with 0% and than there is 40%. And what does it means at all. Is every magic ability only temporary a goes and goes away?...I hate magic
when you have an armor it says ac 5 (5) then 40% magic availabe. 40% is how much percent you get of the number in the brackets. And that percent depends on what is your actual magical aptitude
Magic Power Available (MPA) is based on your magic aptitude. At 0 aptitude you get 50% MPA. It raises as you increase your Magic aptitude and lowers as you increase your tech aptitude. Based on how powerful the magic item is it may not get to 100% until you are a very powerful mage. So if the numbers are too low spend CP's on spells.
Or if you don't care about your alignment, equip a Dark Helm a few times. That'll get your MA up to 100 with a quickness.