Magic

The environment and other life provides the mana for the mana pool. The mana pool provides mana to all the casters on the field. When there is no mana in the mana pool any spell casting is a overstrain. Overstrain can pull mana from different sources Black mages pull mana from tainted life or the suffering of the pure, red mages pull from the emptied space around them cuaseing distortion and warping of the fabric of reality. The blue mage uses tools and trinkets to ease the strainstrain. White mages share the burden with a collective. Never without pain but never overwhelmed.