Here is the first part to YMYV2!  I wrote this awhile ago but I'm changing it up a bit so it won't be like the first version of this, just an FYI.

Mount Justice

"Nice one, Robin!" Nightwing called over to his younger brother, Tim Drake, the new Robin, as he defeated Superboy in a sparring match.

"His center of balance was off, wasn't too difficult." Tim shrugged, high fiving Dick anyways as he walked over to stand next to the rest of the team.

The Young Justice squad had changed over the past few years, seen some members pass in the line of duty, seen some leave and come back, but the current gathering of the team consisted of Nightwing, Robin, Wonder Girl, Superboy, Miss Martian, and Impulse. The other members were away on a mission, leaving these six behind to train and over see the mission from the mountain.

It also left those six behind for when a giant blue star appeared above the mission floor, depositing six vaguely familiar teenagers on the ground in front of the team with a loud thud.

"Okay, America, next time you do that, give us a little warning, mmkay?" The girl clad in a purple jumpsuit complained, rubbing her sore back.

The Young Justice members all got into defensive positions, that is, until M'gann realized who they were. "Kate? Kate Bishop?" The girl in the purple looked up, eyes narrowed until she saw where she was.

"Oh, my god. America, how did you know about this place?" She stared at the other girl, the only one to land on her feet, who just shrugged. Kate narrowed her eyes, her head swiveling to stare at the boy who was significantly younger than the rest of them. "Loki, was this your doing?"

"I'm not the one who creates star-portals, Bishop." The child, Loki, answered with a knowing smile. "America must've picked up on your connections to this dimension and created a portal here. I had nothing to do with it."

"Wait, Loki?! As in the one who caused you to come to our dimension in the first place?" Conner looked concerned, staring at the three familiar faces. "Where are Tommy, Eli, and Cassie?"

"Tommy left the team when we were broken up, same with Eli, and Cassie...Cassie died." Teddy answered, Kate's flinch not going unnoticed. "Your team looks different, too. What's up with that?"

"Kaldur, Artemis, and Wally left. This is Robin, my brother, Wonder Girl, and Impulse, Wally's cousin." Dick supplied the Young Avengers with an answer. "Care to explain why Loki is with you? I thought he was an enemy?"

"He is, but he's with us-" Billy was cut off by America Chavez, the new girl, shoving her way forward.

"He's here so I can keep an eye on him. He's the reason we're in a mess -again-"

"Actually, that would be Wiccan's fault." Loki supplied smugly, earning a glare from all of his teammates.

"What I think my friends are trying to say is we could use some help." The last new face spoke up.

"I'm sorry, who are you?"

"I am Noh-Varr, Kate Bishop's boyfriend." He stated proudly before remembering their purpose. "So, what do you say? Will you help us?"

The Young Justice squad exchanged a look, staring at Dick for an answer. Dick sighed, opening his mouth to reply. "Our answer is-"

"Wait, before we give you a definitive answer, why don't you tell us what is going on, maybe?" Tim hummed, crossing his arms over his chest and looking at the Young Avengers. 

Billy let out an awkward chuckle, rubbing the back of his neck. "Ha, well, you see, that is kind of a funny story..."

"Billy here was trying to bring back my dead mother and accidentally unleashed a universe devouring creature called Mother who is now bonded to us and we are on the run from her. We can't stay in one place too long before she finds us. Which sucks because Billy needs to reach his full potential as the Demiurge to defeat her but he can't practice his powers if we are constantly on the move." Teddy answered, looking to the Young Justice squad.

The team exchanged another look amongst themselves. "And...how exactly will we be able to help?"

The Young Avengers shrugged.  "The more hands we have on deck fighting Mother while Billy practices his powers, the better of a chance we will have against her."

"This...doesn't exactly sound like it concerns us. Sorry."

"Did we not help you with your problem with the Light?" Kate scoffed.

"Yeah, after Billy made it worse!"

"He was under their control! Whatever, America, let's go. I thought they were true heroes, but I guess they are just posers."

America nodded, turning and walking a few feet away from the group. She pulled her fist back and punched the air, creating a star shaped portal. She looked over her shoulder at her friends. "Our new destination aw-"

A gooey tentacle reached through the portal and grabbed America, dragging her through and cutting off her sentence mid word. The two teams stared at one another, unsure of what just happened.

"Um, what was that?" Cassie asked, right before a tentacle grabbed her and ripped her through the portal.

"Wonder Girl!" Tim yelled.

Loki smirked, turning to the Young Justice team. "I guess you are helping us whether you like it or not."

Conner glared at the Asgardian. "If you are behind this -"

Loki rolled his eyes, walking towards the portal. "Yes, because I would orchestrate a tentacle monster to attack my friends just to get some fourth rate teens to help us with our Mother problem. Please. I have more class than that."

"Do you?" Billy mumbled, watching the young god jump through the portal. He turned to the Young Justice team with an arched brow. "Are you coming?"

The remaining teens quickly decided together to go after their captured comrade, following after the Young Avengers on the quest of a lifetime.