Words don't do justice for my memories of the next bit; pretty much every language there is contains some inherent assumptions, such as that the person doing the speaking maintains a consistent level of sapients. So even trying to fit my memories into words is going to give an entirely false set of impressions. But I can't get away with not offering any description at all, so:
I remember the bright light. My memories around it are somewhat confused and contradictory. But after some point, those memories settle down into a reasonably coherent narrative: I ate. I pooped. I slept. I didn't think. I hung around some other cows. Time passed, without being noticed.
Even that much, I'm already wincing at how little the words reflect what my experience was like. So I'm going to do two things. One, I'll skip ahead to where my thoughtless, endless now changed; and then I'll describe my best reconstruction of the events I was zoned out of.
After some time, a period I was unable to conceive of, let alone measure, some not-quite-cows wandered through the cows I hung out with. I noticed a blanket or something on my shoulders. The not-cows nudged me away from the others, which I didn't like, and to a basket of oats, which I did enjoy eating. There were some strange noises and lights... I experienced some rather strange physical sensations, my entire body changing at least somewhat...
... and with a flash, both of light and of inspiration, I started thinking properly.
My reconstruction comes mainly from things the Mikoyan's crew told me, as well as some other reports, and my own estimations and interpolations.
The "Peace, Love and Harmony" spell wasn't quite the magical equivalent of a nuke - but powered by the Ursa Major bones, and possibly altered by the Lady's Cloak, it was at least a MOAB-level magic. That fleet full of viking warriors intent on raping, pillaging, and general mayhem got turned into... well, hippies, for lack of a better word. The ships I'd encouraged to come fight the invasion arrived to find a bunch of would-be settlers, instead, and after some confusion, eventually got them to spread around all of Thule, to establish homesteads and start farming undeveloped land.
There was no sign of Dirk Steel. Given that he had some sort of anti-magic effect, he might have gone into hiding after his fleet disappeared. Or, if his anti-magic was through the use of black rock of the same sort we'd found in the giant crevice, which has a finite capacity before exploding, there might not have been anything left of him other than a few feathers.
My conclusion about what happened to me... is that some combination of my will directing the spell, the overload of raw magical power, the cloak, and the magical-neurological properties of my species... gave me a super mind-numbing zap, like the ones I got from forming a circle with other Equestrian cows; and by the time that wore off, my body's magic had already run out for long enough for my brain to shrivel up like a raisin.
As for the Mikoyan and its crew... well, maybe it would be best to show what I learned, from the point of the second flash.
I wobbled on all four hooves, as I looked around. There was Red, and Micro, and the other two unicorns of the crew, Tranquil and Berry. I was standing on something like some plywood sheets, on which were carved a magical circle, lined with diamonds. The Lady's Cloak was back on my back. The Mikoyan was floating off in the distance - back to the bare planks, instead of covered in flowers, and now painted a matte black rather than merely varnished.
I started to say something, but my throat was raw, and my lips and tongue were clumsy. Not quite as clumsy as a beak, so after a couple of tries, I said, "I thought... I ordered you... to keep on... the mission."
Red and Micro looked at each other... and, rather to my surprise, both broke out into broad grins; Red even gave Micro a hug, thudding her on the back. Tranquil and Berry high-fived (high-hoofed?).
I raised an eyebrow, and asked, "How... long?"
Red pulled herself back from Micro, and looked up and down at me. "It's been... two months since we lost you. We've tried getting hold of Svalinn, but, well, hit a snag - one we think you might be able to get through. So we started looking for you... do you have any idea how many herds of cows there are here?"
I shook my head, then tried, "How... find?"
"Well, after a few false leads... Blanche remembered the cloak. It's supposed to find its way back to its owner, so after we found it again, we've been trying to give it a chance to find its way back to you. We got a few false positives at first, but... well, here you are, talking to us now."
I nodded, then frowned. "Where... Blanche?"
"Ah," Red said, and looked away. "That's... a bit complicated."
"No it's not," said my lips, without any volition from me. "Just tell her, already."
I blinked a bit at that.
Micro piped up, "You have to understand - for all intents and purposes, your mind was gone. So we've had to use... extreme measures to rebuild it. We needed to physically reconstruct your brain, and, well, we've only been able to find one piece of magic that can do that."
I glared at her. "Don't... tell me... forbidden... spell... forty-seven?" I was referring to one of the secret tomes I'd gotten from the Pillar family, specifically a spell which allowed the caster to reshape the target's body in almost any way imaginable - as long as another body was merged into it at the time.
My mouth moved again, "Don't be mad at them - I volunteered for this. We improved on the version of the spell from your notes - I, well, my brain, is attached to your spine, somewhere near your kidneys. Everything you experience, I do - and I can move our body, too, if you're not moving it. We can get me back out of you, by casting the spell again to merge me into another body, like into an ordinary cow's, and reshape it to be a pony and put me in charge of it. In the meantime - you can think of me as your backup... I'm sure you can think of a bunch of clever plans involving me being hidden away inside here, where nopony would expect me to be."
I closed my eyes for a few moments and rubbed between my horns. "I have a headache," I announced. "Maybe more than one. So... what's the problem... you need me for... that this is the easiest solution?"
"Ah," Red said. "That's also complicated. Are you sure you're up for all this?"
I looked behind me, at the herd of cows I'd been part of for... months. I kind of wanted to go back and join them - they were a nice bunch, comparatively speaking. But... "Vacation's over," I said, as much to myself as to the others.
"Right," Red nodded. "Well - we know where Svalinn is. Some of us have even managed to see it. But... it's kind of hard to describe - none of us have been able to get it. And all of us who've tried - none of us describe the same thing. The Round Table's consensus is that it involves some kind of customized vision - heart's desire sorts of things. When Stoke Red and I went in... we saw ourselves in charge of an airship fleet - and then we were back outside."
Tranquil piped up, "I saw myself as a seapony. Firebough saw himself as emperor of all the Northern Wastes. Half of us won't talk about what we saw."
Red said, "To be honest, we're kind of grasping at straws, with you. But since you had that mental duel with Lady Kohl, and were able to think your way through the mind-affecting spells on the Pillars' books... it seemed worth trying to find you again, to see if you could do something like that again."
"Not to mention," Blanche said with my mouth, "even if you can't, I didn't want to give up and head back to Equestria without you."
I tried to think through the implications of that - and my thoughts felt fuzzier than they used to. I decided that I probably wasn't all the way back to snuff, after so long without thinking at all; and that I should take the time to run through my checklists, to compare how well I thought now to when I did similar tests while stuck in the shape of a bird... and see if I could get myself thinking clearly again. In the meantime...
"Need to think," I said. "Sorry - I mean, think better. Feels like I need caffeine. Maybe we should... get back aboard... the Mikoyan? Continue there?"
The ponies looked at each other, gave each other shrugs and nods, and started packing up the gear.
I looked back along my flank, and said, "So, uh... Blanche?"
"Yes?"
"When you say... you experience everything I do..."
"We've figured out that a sleep-wand can zap one brain in a body without zapping the other."
"... Glad you've been thinking ahead. Er... how, exactly, did you figure...?"
"We've been practicing the spell on other cows, to figure out how to get it right, and how to improve it."
"How much... did that cost?"
"Er, not much at all."
I hung my head. "So... you've been using... a black flying ship... with technology beyond the locals' ken... to abduct cattle... and perform experiments on them?"
"Pretty much."
"... Remind me to give all of you a stern talking-to about that... and to wear my black suit when I do."