From Ars Magica
Mana is the main resource used for all spells.
Mana regenerates is tick based, and is calculated with the following formula:
regenTicks = ticksForFullRegen * (0.75 - (0.25 * (magicLevel / maxMagicLevel))) regenPerTick = mana / regenTicks
At level 1, this makes mana take 8940 ticks (447 seconds) to regenerate, giving a regeneration rate of 0.227 per second with the amount of mana possessed at level 1.
By level 50, mana takes 6000 ticks (300 seconds) to regenerate, giving a regeneration rate of 100.506 mana per second with the amount of mana possessed at level 50.
Increase With Level
Mana is completely filled when you increase your Magic Level
Mana increases with level using the following formula:
mana = (magicLevel ^ 1.5) * (85 * (magicLevel / maxMagicLevel)) + 100
This gives a range of roughly 100 mana at level 1 to roughly 30000 mana at level 50.
Not Enough Mana
If you try to cast a spell and do not have enough mana, the mana bar will flash purple in the UI briefly.