The Shiftius Curse is a curse that grants the ability of shapeshifting to it's host, however it is called a curse as very few can control this ability and instead are damned to a life of shapeshifting at random.
The Shiftius Curse is an ancient curse in the Milky Way Galaxy. It's origins are unknown.
Details of the Curse
The Shiftius Curse is passed on to a new host in two ways, one is on random occasion a being will awake with the curse. The more common case, is that two beings of the same host species pass the curse onto a new host, while alleviating themselves of it.
The Curse first grants the host the ability to breath in any atmosphere. The Curse then detects the biosphere of a planet through it's atmosphere the host is currently breathing. Then, all species that live in that biosphere are "unlocked", and the host can shape-shift into any of those species. The host is always able to shift back to their original form. This means, if the host is breathing an atmosphere that does not contain any life, then they will not be able to shift into any form. Any clothing/garments worn by one form will disappear when shifted out of that form, but reappear the next time they shift to it.
The Curse is infamous as almost every being in the Galaxy cannot control it, and will randomly shift, with frequency ranging from once a year to constantly shifting. Only two known beings, Shift and Querentiano can control it, granting them extraordinary abilities.