How Icons Work
As long-time readers know, I've been struggling with the idea of Icons for a while now, and today I think I've finally figured out how they're going to work. This is a synthesis of some ideas that I've had before, fade's original concept, and my recent study of ancient Greek philosophy. Comments are, as always, welcome.
Each Icon must, at creation, choose a First Principle, known as an Arche (ἄρχη, pronounced "AR-khay"; the plural is Archai, ἄρχαι, pronounces "AR-kheye"). An Icon's Arche is a lens through which he views the world, and with which he attempts to impose order on his surroundings. Each Arche is an observation - perhaps necessarily flawed, but comprehensive nonetheless - about the fundamental nature of the universe; examples might include "everything comes from and returns to water" or "everything either is or is not, and nothing can change between the two", to take a cue from Greek philosophers. (Archai may have complex consequences, but they are always at least stated simply; as a guideline, if an Arche requires more than one comma, or spans more than one sentence, it's too complex.)
An Icon's Arche provides not only his perspective on the world but the abilities granted to him by his Relic - and the limitations on those abilities. Each Icon can manipulate the world based on the way his Arche interprets it; for example, an Icon with the Arche "everything is constantly in flux" might be able to sprout wings to allow himself to fly, or to transform the gun in an opponent's hand into a banana. In exchange, however, the Icon must not use his Arche to prevent something from changing, or to maintain the status quo (or status quo ante); acting against his Arche is not only difficult but dangerous. This does not mean that the Icon cannot use his Arche in this way - but if he does, there will be consequences.
While an Arche is often an Icon's best effort to impose order on the universe, it is almost always imperfect, due to limitations of perspective. Frontier's philosophers call these imperfections ἁμάρτημαι (ἁμάρτημα in the singular, pronounced "haMARteima"/"-meye"), but most who know about them simply refer to them as Flaws. Each Icon's Arche has a Flaw that manifests when the Icon successfully uses his powers in a way that contradicts his Arche. The penalties to the Icon range from mild to devastating depending on how badly his actions violate his First Principle, but each violation always causes the loss of the Icon's supernatural abilities, at least briefly. (In game terms, the Icon's powers should be unavailable until the end of the scene.) In addition, the Relic will backfire on the Icon, which generally involves the Icon's own powers being directed at himself, to negative effect. In nearly every case, the effects of an Icon's Flaw is temporary, lasting until his abilities return, but more catastrophic Flaws can impose permanent disadvantages on the character. (If the Icon has used his power to counter his Arche, and received a critical success, the Flaw always imposes a permanent disadvantage!)
For example, the "Flux" Icon above has used his powers to give himself wings, but while he's in flight, he feels the wings begin to disappear. He quickly tries to maintain the wings, and in doing so, invokes his Arche's Flaw - by maintaining the status quo, he is denying that all things constantly change. He is successful, so the wings remain; but he is suddenly cut off from his power, and until he re-establishes his ability to use them, he will be flighty and mercurial (even more so than usual!). Alternately, the Flaw might have manifested physically, as a constantly-shifting appearance, or as the Icon losing control of his emotional state - or as simple unluckiness, as the Icon loses his ability to accurately predict the consequences of his actions.