Liao is a fictional substance created by Frank Belknap Long for his short story "The Hounds of Tindalos", where it is depicted as a drug that allows the user to mentally "travel" through time and space, seeing visions of ancient places and eras.
Description[]
According to Halpin Chalmers, Liao was used by alchemists in China many centuries ago. The great philosopher Laozi used it to see the Tao, which permeates all things. It is practically unknown in the western hemisphere.
The drug is consumed in pellets. The first effect is a sensation of darkness, during which some objects fade from the user's sight while others remain visible. Afterwards, the user is flooded by the sensation of seeing and participating in historic and prehistoric scenes, as if reliving all one's ancestors' lives simultaneously. On the next stage, the user can move through different temporal dimensions, which Chalmers identifies as "curved time" and "angular time". The longer the user remains in trance, the further back in time they can go and the number of "strange angles" increases. If the user peeks through those angles, they might see the creatures that inhabit these dimensions, such as the Hounds of Tindalos, which in turn might become aware of the time-traveler's existence and track them.
Even during a trance, the user remains capable of conversing with other people, and it is possible for the user's consciousness to return to the present if another person violently shakes them.
When he took Liao experimentally in 1928, Chalmers was convinced that the drug itself posed no danger, although he did acknowledge the danger of getting "lost in time" and unable to return without outside help. As he found out, however, the Hounds of Tindalos pose the biggest danger, as they can track the user long after the latter has returned to their own time, and use geometric angles to enter our dimension. (CIRCLE: "The Hounds of Tindalos")
Liao might be derived from the Black Lotus. (EXP: "The Madness Out of Time")
Behind the Mythos[]
The effects of Liao are similar to those of the unnamed drug taken by Michael Hayward in "The Invaders", by Henry Kuttner. However, in Hayward's case, the mental time travel attracted the attention of a different kind of extradimensional predators: namely the Ny'ghan Grii, as opposed to the Hounds of Tindalos.
The effect is also similar to that of the crystal from Clark Ashton Smith's "Ubbo-Sathla".
In another Smith story, "The Plutonian Drug", the titular stimulant expands the user's temporal consciousness, but is distinct from Liao in that it only allows the user to see themself a few hours into the past or future, as opposed to seeing one's past lives. Nevertheless, some Mythos works have referred to Liao as the Plutonian Drug (EXP: The Encyclopedia Cthulhiana).
Liao is also similar to the taduki drug from H. Rider Haggard's Allan Quatermain series, which is featured in the Mythos crossover story "Allan and the Sundered Veil", by Alan Moore.