More on eminent and inner light
Depending on the kind of spell one wants to cast and at what strength, spells will either use eminent or inner light. Whether or not the light is consumed or returns to the user also depends on spell type and strength.
Spells with temporary and/or weaker effects tend to be cast using eminent light. Stronger or more long-lasting spells using eminent light will consume it instead of returning that light to the user.
ID: Generally, telekinesis used on small objects does not consume eminent light. Telekinesis used on large or multiple objects will consume eminent light.
Once all eminent light is consumed, the current spell being cast will cease. Depending on the nature of the spell, it may stop immediately or slowly fizzle out (or some other behavior).
ID: Once all eminent light has been consumed, cosmetic spells tend to end immediately. The effects of something like a glow spell, however, may slowly die down instead.
Inner light is used in spells with stronger or more long-lasting effects. Unlike eminent light, which can return to the user depending on the spell, some amount of inner light is always consumed in the spells that call for it. For spells requiring a relatively small amount of inner light, eminent light can be used instead. This option is only available to stronger spell casters, who already have strong inner lights.
Spells with more specialized effects (such as influencing the weather) will always require inner light, and the cost cannot be bypassed with eminent light.