Spark

The spark is a pseudoparticle that contains a fae's "essence" or "soul". It provides them their morality and personality: their superego.

Every fae's consciousness is a result of the combination of a spark and a body. In a physical sense, the spark unlocks functions in the brain that allow for a higher state of consciousness. If the spark and body are separated, this functionality is lost, and neither are conscious. Both are acting like an automata, with the body working on instinct, and the spark working on patterns. Neither are experiencing, but upon reuniting (or upon uniting with a different body or spark), the fae receives memories of experiencing everything as though they were in both places at once, their "ego" filling in the gaps. To a fae, this feels like a very similar experience to dreaming.

Physical Properties

The spark is a complex exergetic organism presenting as a quasiparticle of topological defects within the æther. It typically exists in superposition, called an aura.

A spark produces very faint, usually imperceivable light. This light is brighter while the spark is focused. When resolved, it can even be too bright to look at.

Power

The power of a spark, which can be physically measured by its complexity and size, determines how rapidly it can affect the æther. Simply being diffused within a body strengthens a spark enough to negate its natural decay, though a resolved spark can be weakened if damaged.

Physically, the power of a spark correlates most to its complexity and size, which can be measured when resolved.

Outside of purely scientific descriptions, power often also includes more subjective traits, such as how well "integrated" its patterns are, or how much a fae knows about sequencing.

A fae can strengthen their spark by developing patterns, which makes the spark more complex. Fulfillment and actualization, as well as building habits, creates patterns. A resolved spark "acts" in accordance to its patterns, so a stronger spark is capable of more complex actions when resolved.

Maslow's Hierarchy of Needs is a decent model to determine what may strengthen a spark more. Physical needs like food and water are just enough to stave off natural forces that otherwise weaken sparks, while intimacy, achievement, and self-actualization strengthen a spark much more.