Well, Xenopedia says the Empress is a caste. Queen Xenomorphs have three spikes on their crests, but when a Queen becomes an Empress, they'll have five spikes on their crests. Some Empresses grow wings as well.
the empress can still not be technically a caste, since it was not born with her changes or still transforms completely.They are also just as strong as before. I've also read on this wiki, and it is what i saw. as for wings, they only come when a facehugger empregnantes a flying creature and is not a empress-unique ability.
yep, here's the proof: she is like, twice the size of a queen. she cannot be born directly, so a xeno must mutate into one. she has freaky mind controling powers (not just her own race, but the others like predators and humans as well). she is also the only one capable of producing the red, giant facehuggers from kenner. She can make people have nightmares about xenomorphs without even knowing what they are. They also can seem to be the true supreme rulers xenomorph prime. they are often protected by elites guards. they also seem to have emotions like rage and hatred, as seen with the battle between a red one and a regular one. One major psysical difference is that they have tendrils on their heads, similar to the predalien's dreadlocks.
whoo.... crap. Aliens are bad enough! huge, fast, nasty.... add to that Predator's bad temper and bad-assery... hmm... i suppose Predalien doesn't maintain the Pred's sense of fair play either... damn.