'Travelers' are magicians who possess the psychic ability to read the minds of others, and are able to transport themselves (and others) to different locations, including different and distant worlds.
The ability to travel between worlds, however, is not limited to the physical. The mind of Travelers is constantly invaded not only by the thoughts of bystanders, but also those from other worlds. For this reason, disciplines such as meditation are taught to Travelers along with Psychic Magicians, although some resort to the use of pills and drugs.
Travelers are regarded as the most powerful and knowledgeable of all magicians.
While Travelers have the opportunity to see things few will ever experience, those who do not learn to hone their aim can end up making deadly jumps off-target, landing deep underwater, or on the peek of Everest, or outside the Earth's atmosphere. There are some sigils and tattoos that help focusing the Traveler's power, but even so rigorous practice and training are required to build precision.
However, Brakebills has never had more than one Traveler student at any given time, so the faculty group Travelers with the Psychics because of their shared ability to read minds. Most often the only training available is limited to the theoretical, leaving young Travelers with no option but to learn via trial and error. For this reason, the general life expectancy of Travelers is typically rather short.
Some see Traveling as a curse, and opt to magically tether themselves to Earth, practicing Astral Projection instead of actual physical Travel.
Other Travelers embrace their high-risk ability with a devil-may-care attitude, even taking others along for a ride, acting as a human bridge to the multiverse. Whether they like it or not, Travelers alone holds the key to things the earthbound individuals cannot even fathom.