A drug that is used in conjunction with a Dreamer Console for WATI's Project Alchera. It is injected into the user's bloodstream and usually works within a few minutes. Morpheus is essentially a strong sedative and hallucinogen used to induce dreaming. Overdoses of Morpheus, or too much over a short period, can cause heart failure as was the case with its testing on Faith. Morpheus was also being used as a treatment for Eingana while it was experiencing critical system problems.
In The Longest Journey, a designer drug called Amathin or 'Rapture' is often mentioned in connection with the weird goings-on in Venice; April Ryan wonders if the 'waking dreams' people are seeing could be caused by rapture gas. It is possible, therefore, that the hallucinogenic compound in Morpheus has an Amathin base.
Morpheus is named, not surprisingly, after the Classical god of sleep and dreaming (as is the drug Morphine). Specifically, Morpheus was responsible for images of humans in dreams (his brothers looked after animals and inanimate objects), and had special responsibility for the dreams of kings and heroes. In Neil Gaiman's comic Sandman the titular character is often referred to by this name. Ragnar Tornquist has cited the comic as one of the main influences on the TLJ series.