Energy

Ever since the cataclysm, magical energy has been in short supply in the world of SpellMaster. As a matter of fact, the total, world-wide amount of energy is rather limited, and all magicians tap into the same source. The global flow of energy affects all magicians, and it fluctuates constantly.
In response, most magicians have found ways to store magical energy. You will have to find a unique way for your character to accomplish this and roleplay it. He can store it in an item or artifact, or inside his own body, it does not matter. It can, however, serve as a source for roleplaying. A magician who uses an artifact to store his energy can be robbed of it, rendering him helpless. One who stores energy inside his body can not have it stolen, but could suffer overload or drain.

One way or the other, magical energy is gained at four special moments each day - at midnight, sunrise, noon and sunset. In essence, every 6 hours. The amount of energy gained from global magical flow is the same for every magician. The exact amount is fluctuating constantly, though through appropriate magical effects it can be estimated up to a day in advance.
The total strength of the global flow depends on the number of active sources. It is possible for the players of SpellMaster to alter this global flow by discovering or destroying sources of magical energy.
For gameplay purposes, we express the flow in points of energy gained per character, even though it really should be a sum total divided by the number of magicians tapping into it. That is only a gameplay simplification and it serves to make sure energy available does not drop when more players join.

In addition to the global flow, councils can also take control of sources of energy and limit their contribution so only members of the council profit from the source. To express the higher concentration in a straighforward way, controlled sources will add twice their normal amount of magical energy, but only to members of the council controlling the source.

The amount of energy that can be stored is not unlimited, because energy flows, and there is an equilibrium where the natural dissipation equals the regeneration. Every time energy regenerates (i.e. four times a day), the magician also loses 10% of whatever energy he has still stored. So if energy regeneration is 4 points, nobody can store more than 40 energy because at that point, loss and gain will equal out.

Energy can not be influenced by magic in any way. There are no spells nor rituals to increase, slow or change the flow of energy. Energy can also not be destroyed or transferred.

Creating a magical effect uses up that limited amount of magical energy available to a magician. But with training and experience comes the ability to use energy more efficiently.
To calculate the amount of energy used up in a casting, no matter if it is a ritual, spontaneous or a spell, check your experience level in the base used and divide the power level of the spell by it. That is the amount of energy used up.
So if you have a skill level of 12 in fire, casting a Fireball spell or similar effect, which has a power level of 12, has just become possible for you and will result in an energy cost of 12 / 12 = 1
A master of fire, with a skill level of 50 would, only need to expend 12 / 50 = 0.24 energy for the same effect.

Concentration

Magic being an art of the mind, wielding magic becomes more difficult when a magician is tired or exhausted.
The game mechanics is the same as for energy, except that it governs the intent of the spell. So if your skill level in harm is 20, casting a Fireball requires 12 / 20 = 0.6 points of concentration. An advanced practicioner of harm spells with a skill level of 40 would only need 12 / 40 = 0.3 points.

Resting is the only way to recover concentration. Every hour, your character will automatically regain one point of concentration, just like he gains an experience point. You can not be more than fully rested, however, so concentration can only ever reach a maximum of 20 points.