Om-Tsor was a drug derived from Rubasdpofiaew, a plant that originated on Tau Ceti Minor. The plant had white petals shaped like butterfly wings, and lowered the temperature of boiling water drastically on contact.
The drug give the consumer telekinetic powers. The nonsentient brasdpods of Tau Ceti Minor used it to help them catch their food. It normally did not affect sentient beings, but it did work on humans.
It somehow got to Earth and was discovered by monks in Nepal. They named their monastery after the plant, which they called Om-Tsor, meaning Miracle Flower. They burned the plant when the Chinese invaded to keep them from using it for evil ends. However, some of it escaped destruction and made it into the wider world. Its misuse in the late 1960s by the Revolution Man nearly started World War III. After the Revolution Man was stopped by the Eighth Doctor, (PROSE: Revolution Man) the remaining Om-Tsor was taken to the Vault. Combined with pieces of the Web, it was used by Owain Vine and William Bishop to astral project themselves back in time. (PROSE: Beast of Fang Rock)