Elin:Spoiler/Faith

Ehekatl's School of Magic

The relevant code relating to the randomized mana and stamina costs is as such:

if (a < 0 && BaseStats.CC.HasElement(1330, 1))        {            a = -EClass.rnd(-a * 130 / 100 + 2);        }

This means that if there is a mana or stamina cost, the new cost is determined by taking a random number between 0 and 1.3 times the original cost plus 2. So in a case where a spell has a cost of 40, it would be randomised between 0 and 54.