What is the Event?
No one really knows.
All that is known is that at some point in the distant past, a massive, pan-cosmic event occurred that changed everything forever. Before the Event, life was considered "normal" (at least on Earth); there was only one known universe, humans believed they were the only sentient species (and quite possibly the highest form of life), and they thought that (for the most part) they had a pretty good handle on physics and how things worked.
The Event changed all of that.
The Event destroyed countless lives — billions of people vanished from the Earth in less time than it took to draw a single breath. It altered the workings of physics, changing the fundamental nature of space and time itself. It nullified almost all technology instantly and altered the face of the known worlds. The moon itself was splintered, playing havoc with the weather and the tides, drawing the oceans higher and changing the coastlines of continents forever.
Moreover, the Event sundered the barriers separating our universe and the other universes, opening up rifts and pathways between those worlds. If you imagine three panes of glass, sliding into one another at high speeds, then you will have a pretty decent idea of what’s happening to the three distinct universes of the Apoc, the Klik and the L'na right now.
Our three worlds, and perhaps even worlds beyond, are shattering... splintering apart and becoming something altogether new and unknown. Some, like the Klik, sense opportunity and welcome this change; others, like most L'na, see only the possible destruction of their way of life and the tainting of their once-pristine home.
The worst thing in the world is not knowing. So, while we think we have a handle on what has happened to our homes, we don’t really know what the long-reaching ramifications might be. For For all we know, we could be sitting — living — on a huge, planet-sized bomb just waiting to explode. We simply don't know if our three worlds were the only ones affected by the event. We've seen hints that we're not alone, in fact... and the other things that are out there — the other beings that we’re "sharing space" with — are far less friendly than any Apoc, L'na, or Klik could ever be.
I only hope that we'll be strong enough to resist whatever else comes our way...