Spellweaving is hard on the mind. You have to hold what each effect is doing, clearly, at once.
- The more exact the mental image needed, the more load.
- The more variables you must hold distinctly, the more load.
- Hold too much and the spell fizzles: it fails, the energy is spent, and it must be cast again.
A variable spell can switch between effects at cast time, but using it at full capacity is costly in both mind and energy. Alternate forms are exclusive: one form per casting.
Aiming the same effect at a different target does not add load or count as a new form. Only changing the form or the type of force does.
Bigger target, more cost. Larger area, more cost. A single-target spell and an area spell are a valuable pair: an area effect does not discriminate, so it hits everything in the room, including what you wanted to keep.
The load rules are based on humans. A mind that is not human may carry it differently.
Innate powers mostly escape it. An innate power works when you know you can do it, will it, and meet the physical conditions. Esoteric casters need little load too, because the rhyme carries it.
The mage who built a spell carries less load than one working from a form they received.