Jak II: Playthrough Part 1: In a Darker World, Jak Talks Bak!

At the very end of Jak & Daxter: The Precursor Legacy, Jak had just used the powers of Light Echo to destroy the Precursor Robot piloted by the evil Gol & Maya to seal them inside the Dark Eco Silos.
Then after collecting 100 (or 101) Power Cells, the duo, along with Kiera and her father Samos the Green Sage, unlocked a gigantic rift gate.
Somehow, the four of them were able to bring it all the way back to Sandover Village, and then Kiera built a ride so that all four of them could see where the rift would lead to.
At Samos' call, Jak started the ride, but then something terrible happened...
A huge wave of monsters flew out of it and started taking over the entire world, including an even bigger monster that seems to be after Jak. Somehow, Samos was wondering about this...
The ride was then unleashed, sending them all into through the gate.
But soon afterwards, their ride was destroyed, splitting up the team. Samos parted ways from Jak with important advice...
"FIND YOURSELF, JAK!"
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After separating from Kiera and Samos, Jak & Daxter crash landed in a new world. A darker world. An almost... futuristic world...
Sooner afterwards, Jak was approached and knocked out by some guards in red, and their red-haired commander. Daxter, useless to do anything about it, ran for his life, but swore to Jak that he would eventually save his life.
Two years later... We see that Jak was stuck inside a prison this entire time, being injected with electrified Dark Eco!
Two years of this, and yet still no results. Baron Praxis here was trying to use Dark Eco to turn Jak into a superweapon for a looming threat known as the Metal Heads, but his constant failure to do this has made him consider to have Jak killed, instead.
After Praxis and Errol leave to deal with more of the threats, that's when Daxter finally shows up. How did he get in there? Let's just say he had some bugs to squash, but that's a story for another time (or rather, another game).
After two years, Daxter really wanted Jak to say something to him...
And... he did. What were Jak's very first words?
"I'M GONNA KILL PRAXIS!"
As Daxter tries to free his friend, Jak just freed himself, by turning into the deadly and dangerous Dark Jak!
He was about to kill Daxter, but once he said his name to him, Jak recognized his furry orange buddy, calmed down, and changed back to normal.
After Jak changed his clothes, it was time for the renewed Jak & Daxter to make their escape from this horrific prison of torture.
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All of Jak's controls in the game are the same as they were in the first game. However, he can no longer attack enemies with his long jump, and despite being able to talk now, he's ironically a lot quieter while you're controlling him. The times only he vocalizes now is if he gets hit or if he falls down a bottomless pit.
Precursor Orbs are now a rare luxury, especially since Power Cells don't exist in this game anymore. You use the Orbs to unlock this game's Secrets, but some of the best secrets won't be available until after you beat the game.
Jak has more health, and you can refill it more traditionally by picking up stored packs of Green Eco, instead of having to gather 50 small balls of the stuff.
Jak can also now collect balls of Dark Eco. Fill the meter all the way up so you can transform into Dark Jak for a few seconds! Don't waste time trying to fill it up while you're in the fortress, though. It won't work then.
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The first mission of this game is to just escape from the prison Jak was in for two years. Daxter will remind you of all of Jak's controls, including the attacks he'll have to use against the boys in red known as the Krimzon Guards.
Eventually, Jak & Daxter escape from the Fortress and make it outside to their new world, Haven City...
Jak meets an old man named Kor, who was also alongside a small kid. He explains to Jak that Haven City is not such a bright place. Even as Jak has escaped from the prison, the walls of Haven City make the entire city a prison in and of itself.
The Krimzon Guard then approached the group, ready to kill them all. Jak was forced into another fight...
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After you kill two of the Krimzon Guards, Jak will automatically transform into Dark Jak. He attacks much faster and more ferociously, and he also takes less damage. Just for this fight, this transformation lasts until you've killed all of the guards.
Jak was not able to handle this Dark Jak form well. It was like he was losing control of himself...
Kor and the kid had to leave for now, but he advised Jak to join the Underground, a team of freedom fighters led by the Shadow that plans to take down Praxis tyrannical grip on Haven City. One of their member's is Torn.
This is where Jak II's adventure REALLY begins! Hope you like Grand Theft Auto, because that's what progressing through a lot of this game is gonna feel like!