Every person has an inner element, or inner elements (usually having one main element and one or two secondary elements). The most common elements are Water, Fire, Earth, and Air, but there are many others, such as Electricity, Grass, and Nothingness, to name a few.
It is possible to harness one's inner element(s) and use them as powers and such, and everyone has the potential to do this, but most "normal" folk do not know how.
Light and Darkness are usually stereotypically linked with alignment, but rather they are basic "elements" that one can choose to have if they put their mind to it (sometimes subconsciously), and are more easily harnessed than Inner Elements.
MCs' Inner Elements[]
Pika: Ice, Electricity, Sound, Disease, Mutation, Arthropods
Joshua: Air, Divinity
Silver: Water
Marilyn: Everything
Gold: Fire
Tessie: Fire; which can range from normal to a dragon's blazes of fire, and also can use Earth, and a few other unnamed ones.
Thomas: Air; primarily in the form of windspeed, and sometimes can use his own reflexes.
Sherbet: She is able to use Water and a small form of Grass.
Sollux: Mortality
Karkat: ???
Mongrel: Disease
Scarlet: Tentacles, Hate
Magenta: Regeneration