Changeling

The Changelings are a sapient amorphous race with outstanding shapeshifting abilities. They are a very ancient civilization, but their history, biology and culture are still poorly known. Most of them reside on a small rogue planet in the Omarion Nebula, located in the Gamma Quadrant, which may or may not be their actual homeworld.

Biology and racial abilities
The Changelings are an extreme example of an alternative form of life. Their natural state is that of a golden liquid, but they are able to take virtually any form they wish, including solids, liquids, gases and even plasma or fire. They must return to their liquid state every 16 hours, although it is probable that this is valid only for still inexperienced Changelings, like Odo.

A Changeling's body is not made out of cells, but of a biomolecular structure known as their morphogenic matrix. The lack of cells means that Changelings are not affected by senescence, being biologically immortal as a result.

They have no sense of smelling and their minds cannot be read even by naturally telepathic species.

It appears that when a Changeling assumes a specific form, it does not only mimic its external appearance, but its ultimate structure as well. When they become rocks, for example, a sensor will not detect them as lifeforms. Also, they are able to morph themselves into fully functional electronic devices. This doesn't make them vulnerable, however, since they can immediately return to their liquid state at anytime. Another interesting aspect of their shapeshifting abilities is that when they morph into a much smaller object, they are able to truly reduce their apparent mass and weight, rather than just compress their volume.

Changelings do not eat or drink, and need no air or any other substance to live. They are perfectly able to survive in space vacuum for unlimited periods of time. Since they need no sunlight either (their homeworld has no sun), it is a complete mystery how they get the energy they need for living.

A widely famous theory explaining both the Changeling's mass alteration abilities and how they obtain energy is that they are able to exist in subspace, as well as in normal space, regularly importing and exporting mass and energy between the two. This idea was first proposed by Star Trek write Robert Wolfe.

History and society
Changelings are an ancient race believed to have originated somewhere in the Gamma Quadrant. Once peaceful explorers, they suffered prejudice from several "solid" races, who were afraid of the Changelings' almost unbelievable powers and resilience.

The Changelings finally decided that the best way to protect themselves was to take control of their surroundings, and thus they founded the Dominion, a major military organization that rules most of the Gamma Quadrant. The Changelings (or Founders, as they are usually referred to) are the absolute rulers of the Dominion, but are still very reclusive and enigmatic, being treated as god-like mystical entities by their servant races. The warriors of the Dominion are Jem'Hadars, an aggressive humanoid species genetically created by the Founders.

Although all Founders are Changelings, not all Changelings are Founders. The most notable exception is Odo, a member of a group of one hundred Changelings who were send out to travel through the galaxy and gather information about other planets and races. After countless years drifting through the cosmos, Odo was found by the Bajorans and ended up working for the Federation as chief of security aboard the space station Deep Space 9.

Most Changelings have little sense of individualism. They enjoy melting themselves together to become part of what they call the Great Link, a gigantic ocean of Changelings in their natural liquid form, all deeply connected together (the result is similar to the sentient planetary ocean of Solaris). The Great Link used to be located on a rogue world in the Omarion Nebula, but this planet was recently destroyed by the Romulans and Cardassians in an attempt to end the Dominion War. No Changeling was killed, however, since they knew about the operation in advance and left the planet before it was bombarded.