Some notes: This is after the season 2 finale of Transformers Prime, assuming Smokescreen did what he was supposed to and left. Also, Ultra Magnus has been with team Prime since the beginning of season 2.
Chapter 1: Rise of a new Prime
Metis Prime POV
Jolted awake from a drawn out stasis, the young Cybertronian crashes toward Earth. Landing without grace, the youngster takes in his surroundings. Strange wreckage litters the ground, the smoking remainders of Decepticon work appears to leave no survivors. Gathering that there was a great battle, he starts picking through the remains. As he starts to wonder why he felt drawn here in the first place, the Autobot spots a shiver in the wreckage to his left. When he lifts away the structure he finds none other than the famous Optimus Prime, nearly out of time.
Optimus POV
I'm being shaken awake. My systems are operating…but…not…for…long. I must pass on my mission.
"Optimus? Is that you? Hello? Can you hear me?" A voice says. I do not know who this young Autobot is, but I know that his spark is pure and that he must be the next Prime.
"You are my successor. Find my team. Save them. Save this planet, and keep the forces of the Decepticons at bay." I whisper, "Please."
Metis Prime POV
Aw, Scrap. How am I going to get out of this one? I think as I stare astonished as the coveted Matrix of Leadership becomes part of my being. I can feel the power of the Primes running through my frame. I watch in despair as Optimus Prime takes his last breath and his spark disperses. My name is Metis Prime, and I must do all I can to finish what has been started here.
(add line break here when on )
"Hold on a sec Miko, I'm receiving an Autobot distress signal from a Comm. link that hasn't been used for some time."
"Could it be a filthy Con trick?"Mico asks with too much enthusiasm
"It could, but it feels…different somehow," replies Bulkhead.
"Oh dude, we totally need to check this out." Miko says.
When the two arrive at the location of the distress signal, they find Ratchet already there arguing with a strange bot. "But how did you open up a Comm. link that hasn't been functional for centuries?" Ratchet asks, exasperated.
"I-I don't k-know, I. Just. Kind of, you know thought that it was necessary." A strange-looking bot answers, seemingly intimidated by Ratchet.
"Yes, but you're not answering my question, how?" Ratchet insists.
"Hey guys!" Miko adds. Both of the bots spin around, their blasters aimed at Miko's head.
"Oh, it's just you, kid" Ratchet grunts.
"Who's he?!" exclaims Miko. "He looks so rad!"
Looking suddenly worse for wear, Ratchet suggests they wait for the other to arrive before explanations are given.
"And that's how I found your leader and became Prime," Metis finishes with little enthusiasm. As soon as he finished talking, Ultra Magnus abruptly transformed and drove away.
Suddenly, Metis optics switch off, and he is hurling through space. When he stops he looks around and, startled, he realizes he is in Optimus's body and his hand is resting on Ultra Magnus's knee. Realizing he is in Optimus's memory core through the Matrix, Metis stops struggling and listens.
"As always it is your choice," Optimus starts, "But please consider the pain I would be in if you were captured." Metris is hurled back to the present with the image of Ultra Magnus thinking about Optimus's request on his mind.
When his sight returns, he looks at the shocked and confused Autobots and announces "We need to find Ultra Magnus. Now."