There is currently a bug in the Savage Dragon mod used in FTB FAM. It causes the server to crash whenever someone breaks, or comes near, one of the crystals on top of the obsidian towers. This means the Dragon fight is totally broken right now and will just crash the server. So, please avoid the End Dragon until the pack gets updated. It will just crash the server. Sorry for the inconvenience. If you desperately need a Dragon Egg or something just let us know. We'll get you one.