For the most part, I won't be doing fan aspects or classes, focusing mostly on canon ones. There will be a few exceptions, like the Waste of Time as a joke, but that will be about it. However, I'm not going to say that the aspects in Homestuck cover everything, because they don't. In fact, there are two primary forces that the aspects in Homestuck ignore: Matter and Energy. Now, it is possible to use some aspects to control these things, but there is no aspect specifically dedicated to it. In this post, I'll be talking about the fan aspect that covers one of these gaps: Form.
Form involves the composition and shape of objects, as well as the creation and destruction of matter.
I won't explain how each class uses form, but I will bring up some ways it can be used, and will occasionally mention specific classes.
Use on self: Changing your own form can be a very useful tactic. Imagine some combination of Mr. Fantastic, Plastic Man and the Wonder Twins. Extending parts of your body, changing their composition and changing their shape. With these abilities you are practically a living weapon, capable of all sorts of attacks. This is likely the primary method an Heir of Form would use to protect himself, making his body tough as steel, or bending his body around attacks from his foes. An offensive class such as Knight or Prince would likely use these powers as well to attack foes with weapons made out of their bodies. A Thief of form might steal body parts from her enemies and give them to herself to fight back, such as copying the organ that generates fire from a fire-breathing foe, or turning her arms into those of a powerful ogre enemy.
Use on objects: Changing the form of objects has many applications. For starters, a hero of Form would likely be an expert at alchemizing items. When they get stronger, they will likely be able to turn one item directly into another. Imagine having the power to turn any old rock into a Warhammer of Zillyhoo. Changing the form of your surroundings might be possible, turning the ground enemies are standing on into a death trap, or turning the area around your team into a fortified base. Once again going back to the Thief, they might use form to steal by simply turning some object nearby into what they want, and turning the original version of what they wanted into the object they just transformed.
Use on others: This one is a bit disturbing, actually. A Rogue might take the wings off of an opponent, and give them to her ally. One might help an ally escape by turning them into a frisbee and tossing them over a chasm blocking your way, allowing them to turn back once they cross. A Sylph of Form would likely heal someone's form, making them the state they were in before they took damage.
Use on enemies: This is where things get really good. The ability to turn your enemy into stone, or feathers, or anything really. You could use it like its use on objects mentioned above, except instead of turning some rock into a useful item, you are taking down an opponent too! Due to form's relation to the destruction of matter, it would be possible to just completely obliterate the atoms that make up a foe, a tactic probably popular with Princes.
Creation of Matter: Something that doesn't really fit into other categories. Creating matter would be useful in and of itself. First, one might be able to simply create any kind of grist they need, continuing the trend that heroes of Form are masters at alchemization. One might also be able to do things like create an anvil over an opponent's head, make a bridge over a gap from nothing, even fabricate powerful items out of nowhere.
As one can see, the Form aspect has many applications and can be quite powerful if put into creative hands.