In 2261 the galaxy was thrown into upheaval in the wake of the last great Shadow War, and the galaxy was caught between ages. It was a time of great change and the responsibilities of the younger races were compounded by the loss of the Ancients. The galaxy - and all within it - was theirs. When a huge and ancient artefact was found drifting in hyperspace by flight crews of the newly neutral Babylon 5, it was brought back to the station to be studied. Bringing the artefact into realspace would trigger a chain of events the Vorlons were only able to postpone at their strongest, that would test the tenacity of Captain Sheridan and his crew to the fullest. Through the artefact they found a dimension they called Thirdspace, and the Harbingers it was home to. This is a sourcebook for the Babylon 5 Roleplaying Game Second Edition that explains in more detail the events that take place in the Babylon 5 telemovie Thirdspace. Such a massive event would send ripples through the galaxy, and this book explains a few of them. Containing rules on how the Thirdsace gate affected Babylon 5 and its occupants, statistics for the deadly Harbingers and the personalities involved, this sourcebook gives readers everything they need to use the events in their own campaigns - if they dare to do so.