Mana is the energy which a player draws on for the use of spells. It is directly determined by the amount of the characters intelligence. Every spell in UO costs a certain amount of mana. If there is not sufficient mana to cast the spell it will fail. Inscription is also depending on the mana pool. Furthermore mana will be drained, if the character is drunken. There are also certain spells that affect the mana-pool negatively: Mana Vampire and Mana Drain.