I do not know much about SW but I did have some ideas last night while sleeping.
1) Magic that does what it is supposed to do but also has some other effect.
2) The "event" opened a gate to a pure elemental realm
3) Areas under cloudy half sunlight half darkness
4) Strange clouds of multiple colors
5) The Navigators equipment does not function at all as they are not tuned to the altered essence here.
6) Being a magical area some mutations may be viable unlike in normal life. You can use some of the standards from post appoc. games if you would like. ie two headed fish, giant head, glowing eyes.
7) People, monsters can have constant spell powers or abilities.
Radiation sickness
Now if it was as Anti Matter bomb you have a whole bunch of other problems as I do not think you would have as much harmful radiation, but I could be wrong but just a lot of energy being released. In this case it could just rip the planer lines so multiple planes could intersect at specific spots. This would create unique creatures as well as many problems as you may not know where one plane ends and another begins.
MDC