The reunion at the Bioship was no more than a small exclamation of surprise at the identity of the person Batman's instruments had picked up. Wally, Zatanna, and Robin had no chance to explain what had happened underground before Batman was ordering everyone back to the cave for an emergency meeting.
As the team returned as asked, they each took a moment to welcome Loki back and apologize for being mean earlier. Their sentiments brought tears to the young god's eyes, and it took much of his self control not to hug them. He felt his small family had just gained a few more members.

Batman cut straight to the chase when Loki and the team entered the cave. He pulled up a picture of what had once been a normal city block but that was now torn in half by what seemed to be a tear in the fabric of the universe. Through the crack was swirling darkness that Loki was all too familiar with. The Void.
"According to the data we've collected," Batman was saying, "this leads to another dimension, or something on a higher plane of existence. Only one thing came through so far, but things will probably come out soon, so stay away." Batman pulled up another picture, this time of the creature that had come in from the Void. Loki frowned. It seemed to be vaguely humanoid, with cloth wrapped around its eyes and most of its body. He did not recognize it, but had a strange feeling as if he'd met it before, somehow.
"What is that?" Wally gasped. Loki shook his head slowly, as mystified as the team.
Suddenly, Batman's earpiece dinged. He listened for a few moments, then turned to the team. "There's more stuff coming out. A ton of creatures with machinery. Like an army or something. The League needs backup." Batman broke off awkwardly, glancing at Loki. Obviously, he wasn't sure what to do with the boy.
"I can fight," Loki insisted, narrowing his eyes. "Let me help."
Batman looked torn for a moment, but then relented. Time was of the essence, and the League seemed to need any backup they could get. "You're going to need to change," the cowled man said finally, gesturing at Loki's hospital gown.
Megan gently took the young god's arm and led him into a side room. She pulled a uniform off a rack and gave it to the boy. "It's one of Robin's," the Martian explained. "You're about the same size."
Loki nodded and she left as he changed. The uniform fit perfectly, but he still felt a bit silly as he placed the accompanying mask over his eyes.
When he emerged, Robin burst out laughing. At Wally's punch he shut up, but still smiled goofily. Loki just glared, although the effect seemed to be lessened by the sheen over his eyes.
"Go," Batman ordered, gesturing at the Bifrost-like circles.
Just as Loki had suspected, the feeling was exactly like being on the Bifrost, except that he was surrounded by science, not magic. In no time at all, they had reached their destination: Manhattan, in a place called New York City. (Wally complained that every evildoer tried to take over Manhattan, but Robin shut him up by beginning to rattle off a list of villains who frequented Gotham but went nowhere else.)
The city was utterly silent. Unnaturally so. Loki shaded his eyes with a gloved hand, glancing around. As far as he could see, even stepping out of the alleyway they had arrived in, there was no sign of life, human or otherwise.
"Split into teams of two, then spread out and help any Leaguer who needs help." Kaldur was whispering despite the emptiness of the place. Loki sidled over to Zatanna, but she was already standing next to Robin. Kaldur walked over to stand by Loki's shoulder. "You have the least experience in battle, so I will aid you." The young god almost laughed. He had the most battle experience of anyone on this team; even though h had never been much inclined to fight until recently, he had still lived in a warrior society for almost a thousand years.
Wally caught his eye and they shared a silent look of mirth.
Wally, Artemis, Conner, and Megan went left, so Robin, Zatanna, Loki, and Kaldur went right. Kaldur took the lead while Zatanna and Robin hung back by Loki's sides.
"My costume suits you," Robin said with a smirk, "but I totally look better in it."
The young god laughed. "Well, it is /your/ costume, after all. I have my own, and if I could access my full power, I would definitely be wearing it instead of this."
Robin gave him a playful punch in the arm.
"So," Zatanna spoke up, "do you recognize that think the came though the...thing?"
"No," Loki admitted, "but I do recognize where it came from. It is a place called the Void, and it is utterly devoid of light or sound. Few things can survive continued exposure to it."
"You seem to know a lot about it," the younger boy mused.
Loki nodded haltingly. "I-I do. I fell...kind of, and landed here."
"Fell from what?" Zatanna asked.
The young god looked at the ground and took a shaky breath. "It is a long story that spans my extensive lifetime. One I do not think can be told in the short time we have. In essence, I fell from the Bifrost into the Void. I was there for what felt like centuries but were only a few months. I think... Actually, I believe I fell into a parallel dimension."
"Wait, /what/?" Zatanna threw her arms in the air. "Where did that come from?"
Loki shrugged. "You did not seem to know anything about the New Mexico incident, and, as you seem to have access to most, if not all, form of human communication, you would have were it to have happened here. Also, while in the Void, I remember colliding violently with something and feeling as if I were being torn apart. I believe it was at that point I came across a dimensional rip." He suddenly looked thoughtful. "Perhaps I left half of my consciousness behind. It seems to be a distinct possibility."
Zatanna and Robin were looking at him with wide eyes. "What New Mexico incident?" the magician asked quietly after a few seconds of stunned silence.
"Hey, you guys coming?" came Kaldur's shout. They hadn't realized they'd stopped. As they ran to catch up, Robin repeated his teammate's question.
"At his coronation, my brother, Thor, made a rash decision. My father banished him to Midgard, or, more specifically, New Mexico. In short, he fell in love with a mortal, earned his reentry into Asgard, and caused a lot of property damage." Loki smiled wryly. He'd helped create the property damage.
"Yeah, we'd probably have noticed if the god of thunder showed up here," Zatanna reasoned.
Loki nodded. Robin opened his mouth to say something, but ended up walking into Kaldur, who had frozen in his tracks. Just ahead was the rip, and it seemed to be expanding as a large, armored, worm-like creature forced its way through. The older heroes attacked it with all of their might, but its armored hide protected it. Loki felt a rush of wind, and suddenly Wally was at his side.
"Friend of yours?" the speedster asked.
"Hardly," Loki replied. "Although it comes from the same dimension I do, or at least another parallel one."
Wally gave the shorter boy a look that clearly said 'we'll talk later', then rushed off to rejoin Artemis in aiding the Flash.
"Robin, Zatanna, help Batman," Kaldur ordered. "Loki, with me. We will be helping my king." The water-powered boy clenched his tattoo-covered arms, grabbed Loki's wrist, and all but dragged him to the side of a blond, bearded man wearing what appeared to be a shirt made of scales.
"Hello, Aqua Lad, who's the kid?" the man grunted, punching the face of the lizard-like creature whose fellows seemed to be coming through the rip with the force of an army.
"This is Loki. He has limited magic and no prior experience, but Batman reasoned that any help is welcome against...whatever these are." As if to emphasize his point, Kaldur used his water magic to cut of the head of a creature that had almost snuck up on Loki. The young god gritted his teeth. He had let his guard down for a second; that would not happen again. Without missing a beat, he pulled a knife from his pocket dimension and let it fly. It hit the eye of a creature about to attack Kaldur. Then, without turning, he stuck another in the chest of a creature that had attempted to sneak up on him.
"'No prior experience', eh?" The blond man chuckled. His laughter died on his lips as a shadow fell across the group. Creatures and heroes alike froze as it came. It was the creature Loki had seen earlier, in Batman's picture. It looked even more terrifying up close. Before anyone could move, it was suddenly in front of Loki and seizing him by the throat, effortlessly hoisting the boy into the air. Kaldur and the other man were frozen in shock, unable to do anything but watch. Beneath the creature's cloth-covered eyes, its mouth was twisted into a grotesque leer. It laid a pale, sickly hand on Loki's forehead and the young god, unable to do anything but squirm weakly in a vain attempt to get free, was unprepared when his mind was assaulted. The presence forced his consciousness down and he collapsed limply.

Images flashed through Loki's head. He was on Midgard...bending others to his will...an item he was after called the tesseract...unleashing a green rage monster on innocent victims...throwing a poor man out of a tower...fighting the creatures...no, he was their leader...they were called the Chitauri, he saw...and then he was fighting Thor...
Why would he do that?
(Because you're a monster)
There was something in his head...another presence...he knew it, it had spoken to him after he fell, told him what he needed to know...it had helped him...so why was it doing this?
What is it?
(I am the Other, servant of Thanos, suitor of Death)
So many memories...of hurting and killing without reason...but they weren't real, right?
(They are. This world you have built around yourself is fake)
Not true, Zatanna and the others are family...
(You have no family, monster. They cast you out)
Not true, not true, he had a new family here, lies, lies, lies...

"Lies!" Loki shouted, eyes jerking open. A powerful blast of pure magic launched the creature—the Other, his memory told him, or at least the memory of the part of him that had been on his original universe. If he thought about it—of course, there was no time to think on a battlefield. He'd think later.
"Are you alright?" Kaldur's worried face had somehow ended up leaning over him. He hadn't noticed he'd fallen.
"I am perfectly fine," the young god grunted, pushing himself to his feet. Kaldur lay a hand on his shoulder to steady him. Loki looked up at the giant, flying worms the heroes seemed unable to defeat. With a jolt, he recalled something his counterpart on that other dimension had seen: a man dressed in a suit of iron firing a blast into the mouth. That seemed to be the only way they could be taken down, unless this universe somehow managed to procure a green rage monster.
"Aim for the mouth!" Loki shouted up at the super-powered beings above him. He felt a rush of satisfaction as his suggestion was immediately put into practice. One worm went down, and then another.
The young god then turned to the rip itself. Creatures were still swarming in, but his newly acquired memories knew how to to stop them: the same man of iron had fired a missile into their home planet-like station, effectively wiping them all out. The portal had then been closed by a shutoff built into the tesseract. But there was no tesseract powering this portal, was there? He would have to find another—
Loki's internal rambling was cut off abruptly by the Other's hand seizing the back of his costume. He spun around as best he could, only to have his head engulfed in the creature's vice-like grip. Out of the corners of his eyes, he saw Kaldur and the other man had been knocked forcibly away.
Something was thrust at the young god's chest, and he instinctively grabbed it. When he looked down to see the scepter (the evil, soul-sucking scepter) his counterpart had been forced to use when attacking this same city, it was already too late.
The last thing Loki saw before he was forcibly sucked into this thoughts again was a wry smile splitting the Other's gruesome face.

No, no, this wasn't good, he had to get back and stop the portal—
(Let them come, little monster. End it)
No, his friends were there—
(You have no friends. You are a monster, a freak. They only feel sorry for you)
That wasn't true, Zatanna and Wally and Robin knew his secret, and they didn't hate him—
(They do not yet know all of it. How do you think they will react when they discover you have tried to kill a whole race, and that you killed your own brother? What then, little monster?)
That was the past, he hadn't been thinking straight, now he was better and he was so, so sorry—
(Do not fight it, Frost Giant. Let it give you the power to take it all back)
No, the scepter would only take over his mind like it had done to him in that parallel universe—
(Let it. Succumb. Let it use you as a vessel to destroy those who stand in our way, and you will rule this realm)
But he didn't want to rule, only wanted to go home and hang out with the team—
(You have no home, little monster. You are neither Frost Giant nor Aesir. These mortals pity your loss, but once you show you are not worthy of their pity, they will throw you out. No place will take you in, you must take a place yourself)
No, but Zatanna had—
(Let it take you over, Frost Giant scum)
No—
He couldn't—
Don't betray your friends—

...

(You are mine now, little monster)