Interlude:

Okay, remember back in Chapter 1, when I thought something about multiverse theories?
Well, what I saw before I blacked out was basically this:

A void filled with an immeasurable amount of bubbles of limited spacetime, with a paradoxical void of unlimited unreality between.
I saw bubbles form, branch, split, and die–not necessarily in that order either.
This ties in very well with my multiverse theories of each universe being the offshoot of a different universe- a "base" timeline, if you will.
As for why I thought about my multiverse theories before I blacked out, well, going through that portal felt really weird, made me delirious and all.

I'd rather not talk about it

Interlude 2: How I knew exactly what to do based on the show

This one is pretty easy to explain. As a brony, I knew exactly where the overall timeline of Equestria was, based on major events. Since I crashed into Princess Twilight's coronation– which freaking hurt, by the way–I knew I was somewhere between the end of season three and the beginning of season four, as seen when I brutally murdered that cragadile.

Yeah, that part was awesome

Chapter 4 Alt Title: What The Fuck Am I Even Doing?
Or: An Attempt to Break The 2K Words Mark

T minus six hours
I was having a pretty good day that day, having finished repairing and replacing everything that I destroyed in my...arrival. And it only took about a month and a half, not bad if I do say so myself.

It took three days in Equestria for me to realize that I didn't get hungry or thirsty unless I wanted to. It took another four days of nonstop working for me to realize I didn't need to sleep.
Despite that, I acted as if I did, mostly because a) sleeping and eating are fun, and b) I didn't want Twilight to use me as a labrat, even if she managed to find out more about my new form.

Never again. Ever.

So now I was living in Ponyville of all places, in Twilight's library. Despite the damage I could cause if I decided to be evil.
I think this is another test of my word. At least I get to do something fun, that being scour the Everfree and get rid of anything dangerous that heads toward civilization.

So far, it's been surprisingly hectic, though one wouldn't expect it. The Everfree is massive, and there are a lot of cities to protect.
Also there's the monsters. Yeah, there's a lot of them. Hydras, manticores, cockatrices, basilisks–literally sixty foot long snakes that can kill with a stare. Not petrify, kill–, giant insects, timberwolves, direwolves, and oh yeah, minor eldritch beings from beyond the edge of the world-bubble.

Slenderman is real, and he is a pony, Slendermane. He's surprisingly nice, offered me tea and cookies.
Nice guy, helps out when he can.

Well, at least I know what happens when I steal shadows. Yeah. I can steal shadows. It's not pretty.

Flashback:
I was patrolling the forest around midnight. The moon was full (as always), the air was clear, and I was dying to sink my teeth into something of boredom. And we all know what happens when we tempt fate in a dark and spooky forest.

RRRROOOOOOOAAAAAAAAAAAAAAAAAAOOOOOOOORRRRRRRR

"Oh shit, a hydra! That's the third one this week! Where are they coming from!?"
While I cursed the forest for being so damn huge, the hydra started wandering in the general direction of Fillydelphia. Noticing this, I panicked a little and grabbed at the beast's shadow, latching on. Then I followed a set of instincts that I didn't know I had and pulled. Let's just say...that hydra's going to have a really difficult time trying to pull itself together again. As in, from the very magic it dissolved into.
Yeah. not pretty.

After that, I started to venture further into the Everfree, mostly to practice against the horrors lurking within, partially because, if you look past the spooky exterior, the Everfree is downright beautiful in a way that's never been seen on earth. It really is that pretty.

I think I'm starting to like this place. Weird.

T minus 4 hours
Two hours after I started patrolling, I was struck with the weirdest idea: what if I tried to see what the void really looked like? With that crazy idea stuck in my head, I tried to teleport where no one had ever teleported before: right outside the boundary separating finite space from infinite paradox.

My first impression of the void was that of the weirdest kaleidoscope I'd ever seen, it was empty, then full, blinding, deafening, yet pitch-black and dead silent at the same time.

My second impression was that there sure were some weird ass things living between universes, many taking the image of the main inhabitants of their patron universe, others being formless blobs of paradox and magic. Oh look, here comes one now, it appears to be...Fausticorn!?

My third impression was very sudden and came almost immediately following my second impression. What was it, you ask? Well...

"AAAAAAAAAAAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUUUUUUUUUUUUUUGGGGGGGGGGGGGHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!"
Pain. Horrible, unending, soul-eating pain. It was so bad you could practically hear the capitals. Oh wait, you're reading this on a screen from a few universes over, you can just see the capitals written down.

Oh, I believe I'm experiencing the kind of clarity that only horrible, soul-wrenching agony can bring. It also appears that I'm delirious again. I think I'm still screaming. How am I even doing that? There's no air here, so it's all fake...isn't it?

I should probably note that–oh look at the pretty colors, why do they hurt so much?– normal creatures of flesh and blood would already be faded and gone. It's only my being made of an absence instead of a presence that's keeping me alive. Hey, is Fausticorn talking?

"You foolish, young shadow creature, why in my name would you do this to yourself," my god, that voice is so pretty, but so wrong at the same time, "if you weren't so young and I weren't so soft towards younglings, I'd have left you to suffer your stupidity. As it is, I gift you with Paradox Survival+3, use it well, for there will come the day that I will ask for repayment. Enjoy your time until then, for I will be waiting."

Oh shit, this is bad. Oh look, my senses are clearing...but I'm still feeling crazy? Oh yes, I guess the only way to comprehend a paradox is to be insane...or be made of a paradoxical concept (like shadows) in the first place.

Good thing I'm both, otherwise I wouldn't be talking to you right now.

T minus 2 hours
I woke up in a hospital, Twilight's face hovering above my own, feeling like shit-on-fire. How the hell did I end up back here? The last thing I remember was teleporting back into the universe wrong and falling into the Everfree as a darkly burning chunk of shadows and paradoxes.
"Umbra, are you okay? You crashed into the Everfree an hour ago, so I brought you here...What happened? Is there something out there that we need to be worried about? Is it some new danger to Equestria? Oh no, don't tell me the Gates of Tartarus have opened! Oh no oh no oh no no no no–"

"Princess, I'm fine. I just did something stupid, so if you'll excuse me, I'm going back on patrol. I'll be back later."
I tried to teleport back to my house, but instead of my normal 'compress into myself' shadow teleport, I got a 'vanish into a crackle of weirdly colored lightning and shadows' type deal. God, what the hell happened in the void? All I remember is Fausticorn saying something about paradox survival or something.

Fuck it, I'm tired. Time to go take a nap.

Ignition in 10...
Two hours later, I woke up with another stupid idea: I was going to visit another universe.
...9...
But how? Maybe I could survive the void, but I didn't know if I could survive entry into another universe, or if I could even hop the barriers. Whatever, nothing ventured, nothing gained, as I like to say.
...8...
With the stupid idea in my head, I immediately jumped out of the universe, folding space-time and poking a hole barely large enough for a photon to pass through, just enough for me to pop through.
...7...
I immediately found myself in the exact place I was before. I looked around for a universe to pop into, each individual bubble ranging in size from baseball-sized to whale-sized. I guess everything in the void gets smaller if it's big enough. What? Anyways, spotting a nice, beach ball sized bubble a few...uh...shit...not too far away, I...drifted?...over and scanned the properties of the universe, just to see what was inside. Oh? It appears to be an Equestria slightly farther back in the timeline than mine. This'll be fun. Special races...Shadowborn? Oh. OH. This'll be real fun now.

After trying to pop in, I got a message that told me to enter a name for my 'invasion plaque' like the thing from Dark Souls, apparently. Shrugging, I entered the name 'Umbra Shadow-Walker' and moved forward.
...6...
Landing near a cave at the bottom of Canterlot Mountain, I saw a glitched out message saying:

'Ư̴̢ͩ̄ͣ̌̐͐͋̂̇̓̚͡҉̭̮̺̞̠͕̘͓̭͚m̴̴̈́ͯ̉͒̓͛̈́̃̈̀ͮͥ̐̂̑̍̈́ͥ͞͡҉͙̭͔͉b̷̥̫̩̤̲̑͌ͥ̂̆̑̍̅͋̚r̂̑͑̓̆̂̽͞͏̡̫̬̠̟̻͍̀͝a͛ͪ̽ͣͫͧ͘͏̴̪̜̪̘͓͜ ̋̊̐̂̅̋̈́͢҉̝̘͇̤̩̦̱̗̹̺̜̤̘̟͎́Ş̵̖͎̗͙͈̦̪̱̇̀̆̂̅͗͂͌ͣͥ̈̇̈́͊ͣͨ̋̀h̶̝̱̯̦͚͂̂̒ͮ̀͘͜͞a͔̖̪̠̖͈̬̤̱̬̞͒̆͐͒ͣ̔̐̆̀ͨ͟͝͞ͅd̶̳̦͕̥̻̬̰̱̩͓͎̝͋̏͆̆͑͗̈́ͧ̉̐̇̃́͝ͅo͂͌ͪͫ͆ͨ͗̌́̉̅͊̃͗̆̐́̚̚͞҉̨̝̫͇̥͉͙̜̗ͅw̶͉̲̮̣̖̬͓̹̬̼̠̬͚̏͌̒̌ͣ̊ͤͩ́ͭͨͤ̇̅ͣ́͞-̴̢̢̥̦̰̹̩͚̜̭̹̤͕̮͂̓̅̒́͠ͅW̨̃ͮ̈́̋͗͌̎ͪ͝͝͏̧̳̙̹͙͔̘̳̖̠̻̭̫̻͈̣͙a̬̼̰̺̞̰̹̻͈̫̭̤̙͕̗̍̐ͤ̕͜ͅļ̴̡͉͕̤̣̪̗̹͉͇̩͉̬͍̙̘͇͇̲̋̒ͤ̈̄̾̓̑ͨ͑̐̈́͐͝ͅk̵̴͈͉͈̈́̐̊̇ͭ̇̄͒ͯ̕͠ͅe̛̍̃̃́̉̐̈́̃͌̐́̚҉͔̠͖̯͉̱̲̥̞͠r̵̪̥̝̞̝̦̦̥̒̈̍̇ͣ͑ͦ͘͜ ̷̢̣̗͕͉̤̬ͯ̉̄̈́ͤ̆̄͊͜͝ͅĩ̸̪͕̯̪̠̫̦͈́̏̾̇͑ͥ̄̇̽̓͗ͬ̋̇͗̏̒̀͞ͅn̅ͣ̍̐̀̎̈́͛ͬ̋̎̑͒͑̓ͫ͛͏̷̢͔̪̱͖̲̜͓̼̲ͅv̛̬̠͔̱͎̫̯͍͔̩̬̅̅̈́̍ͩͭͬ̂ͮ̈́̑̓̀͘a̟̖̬͉̥̺͍̣̠͎̥͇̞̤̙̖ͣͨ̄̓͌ͧͯͥ̈ͮ̀́d̡̙̦͍̣͍̭̪͇͑̾̽ͭͣ͛ͭ̇̃̂̌ͣ̂̿̌͒̚͘ͅę̛̺̹̮͇̖̩̥̭̝͚̺ͬ̂̔͑ͩͭ͛͊̏͐͆̎͐̈̄͒ͫ́̕d̷̵̰̗̫͉̳̞͚̺̟͑ͩ̊ͤ́̚͟͜'

I don't know about you, but I think I may have screwed over the 'invasion' system with my forced entry. Whoops.
...5...
Almost immediately after, I heard a feminine voice say, "The fuck is this shit!? Nocturne, you have any idea what this means?"
Looks like I found a fellow, I guess Displaced is the term...I hope it's a Displaced and not some random pony that I'm about to attack.

I don't really want to fight, being a bit of a wuss and all, but instinct is telling me that resisting the urge to fight only works for the Nudist Invader.

...4...
Clearing my...throat...yeah...I think I still have one...sorta...I announced,"To whoever lives in that cave, I'm going to attack you now. Defend yourself!"
...3...
Launching my arm into a nearby shadow in blade form, I was rewarded with a strangled squawk of surprise and another shadowy being roll out of the cave, frantically dodging my arm...arms...yeah. Did I mention that every time they enter another shadow they multiply? This is hilarious. I'm also keeping the terrain clear by pressing my arm flat against the ground after every 'shadow jump' my arms perform. Aren't I just so nice?
...2...
Oh, looks like she managed to pin my arms. I wonder how, oh yeah, she's also a shadow.
"Hey asshole, I lived in that cave! Did I come to your house and wreck it? No! What the hell is your problem!?"
Cute.
...Houston we have liftoff...
"Hello there. My name is Umbra, and I'll be your invader for today. Come at me with the intent to kill or you'll die. Now DODGE!"
"SHIT!"
"AAAAHAHAHAHAHAHAHAHAHAHA! DODGE WHELP! DODGE! COME ON, I'M NOT EVEN TRYING! GIVE ME A CHALLENGE!"
"SUCK A FAT ONE! SHIT! NOCTURNE, HELP!"
I paused for a moment, expecting another Displaced to pop out of the cave and help, but all I noticed was that the Displaced I was fighting merely had her eyes glazed over and suddenly she was dodging better than before, and using a wider range of skills as well.
Interesting.
"Come now, with that performance, I might as well show you how a REAL shadow fights!"
With that, I sunk into the ground, shifting into my natural form for better control. Immediately, I heard a shout of,
"Shit! Where'd he go!? Nocturne, help me find him!"
It's not going to be that easy, girl. Sending out spikes into the shadow I was hidden in, I was rewarded with a forest of spikes erupting from the shadows all around the area, each reaching about twenty feet up, and then erupting again, horizontally. Rinse repeat. The area is now a writhing mass of shadows and shredded foliage, which only adds more shadows, making more spikes, shredding more scenery, etc etc.

Hoh? It appears that my time is almost up. Grinning, I withdraw my spikes and rise from the shadows, shifting back to my preferred form again. Spotting me, the shadow girl fairly explodes at me, "YOU ASSHOLE! I'M GONNA MURDER YOUR ASS!" Chuckling, I raise my hands in the classic surrender position and drop a bag full of bits and some other random, yet helpful objects, on the ground.
"Good job, you managed to keep me from killing and absorbing you, though you obviously need to work on your attacks. May I ask your name?"
"Wha? Nevermind! What the hell was the big idea with all that? You could have killed me!"
"No time to explain, my time is almost out. Your name?"
"Abyss, why do you need to know?"
"Nice to meet you. I'll be sure to visit again one day. Seeya!"
With that, I was ejected from the universe and back into the void. I guess universes don't like the invasion system. Good thing I got a backdoor access now.
If that wasn't clear, if I get someone's name, I can teleport to them whenever I want, even if they're a universe or two or three or thirty away.

Umbra too OP, must nerf.

Okay, well, now I'm floating in the void again, and all these inter-dimensional horrorterrors are starting to get curious. Good thing that most of my journeys will only be in the area under the jurisdiction of the Fausticorn. Speaking of which, there she is over there!
Hey! Can you see me? I'm waving! Hi! Giving a jaunty wave of a hoof back, Fausticorn continues to patrol her own little universe collection while I reenter my own Equestria.

Apparently reentering a universe is like atmospheric reentry except instead of a fireball, it's a comet of void energy and lightning.
It's disgustingly mind-breaking to look at, and impact still hurts. At least I don't dig up much of a crater.