Elemental

An Elemental is specifically a thaum based entiity, who are either summoned or created through the use of magic. They're said to be summoned in from a realm.

Properties
Elementals typically lack free will, at the whims of the pre-defined reasoning of their summoner. This process creates an AI like entity, whose advancement varies depending on the complexity of the spell used. The vast majority of elementals are created for this purpose, be it as advisors, guardians, or other such similar objectives. However, with advanced enough runecraft, they can be created as their own independent entities, though still imbued partly with some desires in order to give them some definition as a person.

They have to be "bound" with both runic enchantments and magic energy in order to prevent them from dissipating back into their home realm. Therefore, they are often given the ability to absorb energy in order to help them stay alive without the assistance of their summoners. Some also have the ability to put themselves in a stasis of some kind, which is often programmed to happen automatically when their energy reserves are too low. While elementals with a will have a stronger ability to avoid dissipating, it still can happen to them if they're either not able to stay bound enough or if they're attacked.

Elemental Affiliation
What affiliation they have is dependant on both what is pre defined during their generation and based on the creator's own impression of what element means. While they can be the classical elements familiar to those from the Prime Chronoverse, at the heart of it they can manifest in any possible concept. If the summoner believes it's an element, then it can apply to an elemetnal so long as its defined enough to give them a framework to define themselves around.

Other Notes
They can have offspring with any other entity, which seems to run on their own rule of whims rather than anything physical. They create hybrids, who tend to be inherently empowered with the elemental tendencies and abilities of their ancestors.