Vakyrgur

The Vakyrgur are a race of non-Humanoids originally from the Gamma Quadrant, but who migrated throughout the galaxy after the rise of the Dominion, who destroyed their homeworld. According to the Humanoid origins theory, groups of Vakyrgur who migrated to Earth became recognized as the Valkyries of Norse mythology.

Physiology
Vakyrgur physiology is unknown, since they are capable of changing into any form they wish, in addition to being mostly intangible. What is known is that they are capable of breeding with humanoid races, such as the Romulans.