Being

The Beings are gigantic aliens formed from plasma and magnetic fields that have lived at the edges of the Solar System since it first formed. Some of them are interested in planetary life and seek to understand it by performing experiments - one such experiment resulted in sapient life on Pluto.

Anatomy & Physiology
Beings are huge, shapeless creatures made of magnetic fields and the plasma they contain. They are immensely large, stretching millions or even billions of kilometers across. They have a plasma core that serves as a "brain," but otherwise have little in the way of permanent internal structure.

Diet
Beings feed on magnetic fields generated at the Solar System's heliopause - the collision of solar wind with the interstellar medium. They are particularly fond of feeding at the bow shock, where the balancing pressures of the two forces are strongest and the plasma densest.

Reproduction & Life Cycle
Beings reproduce by molding pre-existing tangles of plasma and magnetic fields that they call Protos. Protos are naturally formed inside the Sun and ejected into the outer Solar System. Part of this process is the implantation or creation of a magnetic "genome" within the new Being. Beings can repair nearly any structural damage and are effectively immortal, with the eldest of them being almost as old as the Solar System itself.

Senses
Beings sense their surroundings and communicate primarily by receiving and broadcasting radio waves. They can peer into shorter wavelengths if they wish, enough to see individual humans, but they usually confine themselves to the radio spectrum. Being "speech" consists of low-frequency radio waves, with wavelengths in the kilometer range or more.

Society & Behavior
Despite the immensity of their living space, Beings are so titanic in size that only a few hundred of them can sustainably live in the Solar System. These few hundred Beings all appear to know each other personally. They respect and usually defer to the eldest among them, but Beings sometimes form into factions which may be opposed to this leadership.

Beings usually live in pairs of individuals with opposite electrical charges. This relationship aids in feeding and reproduction, and the opposite charges are very roughly and imprecisely analogous to opposite sexes.

It is implied that other groups of Beings live around most - if not all - other stars in the Milky Way galaxy, and that these groups are in communication with each other.