Vidiians seem to be typical humanoids, but most Vidiians suffer from a disease they call the Phage. Although Vidiian medical technology is far superior to that of the Federation, they are unable to cure the disease, forcing them to survive on transplanted organs and tissues collected from other species. Why the Vidiians are unable to clone healthy organs when cloning technology seems fairly well established in the Star Trek setting is a mystery. Unusually for a species native to this region of space, they possess advanced transporter technology.
The Vidiians have advanced technology, including weapons that allow them to literally transport organs right out of the bodies of their victims. Vidiian organ harvesters aggressively seek vulnerable humanoids from whom to collect healthy organs and tissues. They can be regarded as an immediate threat to any humanoid who crosses their path.