With gusto.

An Aspect is the Knight's main weapon. Usually, a Knight creates their aspect when they're in some sort of danger, or when their own power isn't enough, and is created subconsciously, so it takes the form of something that can get them out of that danger, and is heavily influenced by their situation. A lot of aspects are simply weapons, swords, bows, spears, so on, with special properties, but some Knights summons aspects like wolves, warriors, or even a motherly figure. Unlike other living creations, living Aspects have a mind of their own, and there are even some who decide to leave their creator after the danger has passed. 

Creating the Aspect is the first thing an Evoker does with their power, and after that their power becomes conscious. Unless an Evoker lives to be very old and wise, or is especially talented, nothing they create consciously will be as powerful as their Aspect, and few people ever discover the full potential their Aspect holds. 

There are certain ancient texts and writings that suggest Evokers of old were able to summon a second Aspect, but for the most part these are disregarded as superstition.