Originally considered to be the jewel of the Rigel system, experiments with a variety of artificial bloods forced the evacuation of the planet when these bloods developed sentience, mobility and a predatory nature. Select evacuees only had a few hours notice before being beamed to Rigel III by a series of ships operating a transporter relay.
The planet's vast cities became depopulated treasure-troves which occasionally tempted Ferengi salvage agencies to beam heavily armed extraction teams down to the surface. Still, the Rigelian blood beasts were capable of sensing the bio-readings of living beings, alerting them to the presence of anyone foolhearty enough to beam down to the planet. (Decipher RPG module: Through a Glass, Darkly)