"Hey, keep the line straight, no bunching up! We don't need one of the blasts taking out more than one of us!"
Aw donkey dung... They got another one. I'll be right with you guys, alright?
"LOOK OUT!"
Ow... Owwww... I don't know what just happened, but I legitimately started flying. Well... There doesn't seem to be anypony here so... Uh... Questions, right.
Okay, so, let me get something straight: These worlds don't have separate names. They're all alternate versions of Equestria. They have different themes. This one is about war, which leads me into your second question.
We're fighting against a group called the Nighthawk Rebellion. They have ideals that the land of Equestria should be run by a military rather than a Princess, excuse me, Queen. They believe that the Elements of Harmony can no longer sustain a peaceful Equestria and that a well-equipped group of soldiers would be better as a whole to destroy any and all threats to Equestria.
But to be able to do that, they need to take down the Princess. My troops and I are the only ones guarding Canterlot currently due to a well-timed distraction. If they get past us, it's game over for Twilight and game over for this Equestria.
We're barely holding them back.
As for why I'm dimension-hopping, it was explained in a previous mirror. However, I'll do a rough copy here: A Reality Goddess or whatever she gave herself the rank of, decided to anoint me as a 'Hero of the Light'. She really should've chosen Pinkie because I've done nothing but bring darkness to every world, but that's besides the point.
As a hero of the light, my job is to try to keep the multiverses in balance by doing the dirty work in each world. Thus, whenever a world is either fixed or destroyed... Usually destroyed... I am transported to a different world in the astral storm of the weave. Make sense?
And lastly, the question about Balroth and Niya... Yes, I remember this 'Niya' as some kind of Spirit of Mischief, but Balroth, I haven't heard of.
Anyway, I need to get back to the fight. I'll talk to you later.