Material Components

Mage's spells require the consumption of material components.

Magical energy is liberated from the special materials brought together.

Exactly what these materials are is deliberately vague because they range from esoteric to mundane.

The cost is $1 x the square of the prerequisite count.

If the prerequisite count is 0, then there is not material component.

If the spellcaster lacks the proper components add the prerequisite count to the energy cost of the spell.

Fireball, for example, has a prerequisite count of 4 it would cost $16 for the materials or add 4 fatigue to the cost of casting the spell (making it 5 per die of burning damage).  Note, that in the case of missile spells the material cost is per casting and the fatigue cost is per increment of damage.  It's a lot easier to just have the materials!

No additional materials are required to maintain a spell, but note that the fatigue costs are based on what you used to cast it; so the penalty continues for as long as you keep the spell going.  For spells with a fixed cost to maintain, add the penalty each time.  For spells listing the same or half casting cost; do the math normally from the penalized casting cost.

For ceremonial castings, like enchantments, the lack of components multiplies the time required to perform the rituals by the prerequisite count.

The material components are specific to each spell, but each spell in the prerequisite count includes the materials for the prior spells; so you could raid your ingredients for fireball from the materials for explosive fireball.

Clerical magic, being literally miraculous, doesn't require material components but this is offset by the limited number of spells available and the requirements to adhere to a particular lifestyle.  The Gods are fickle and what they give they may also take away.