Mana
From Ultima Online Forever Wiki
Description
Mana is basically where "Magic" comes from. It is a rechargeable player resource just like Health that is expanded to for Magery Spells. The amount of Mana that a player has is dependent upon their Intelligence stat. The trade is equal. 100 Intelligence grants 100 Mana. Typically a Mage will have between 95 and 100 Mana depending on their template.
Mana is located in the Second bar in your Health bar. Double clicking the Health bar will show your actual Intelligence.
Mana is gained more quickly through the Meditation skill, both passively and when invoked.
Mana regenerates more slowly when wearing heavy armors. It's advised that Mages wear only light armors such as Leather.