To a mage, the mana within them was closely intertwined to the life force that kept each living being alive in the world.
Over doing their magic could be deadly. Using too much mana was equal to bleeding to death.
Henry had learned this from all the time he spent with mages in the Duke's Tower while they waited out the floodplains. It was also why the situation in Idona felt all that much more dire. If the mages ran out of magical stones or magical orbs, they would then have to rely on only their mana.
While there was audible chaos happening outside the magical barrier that surrounded Idona, those within braced themselves for the worse. Many hoped they wouldn't have to use anymore of their mana but they were intent on keeping their sanctuary in Idona safe for future generations.
