Jak 3: Part 31: Into the Sewers #3
4After clearing out the KG cargo, Jak & Daxter return to Freedom League HQ. Count Veagan (Veger) followed closely behind him, laughing at Jak and his friends for trusting him and his Dark Eco powers with reaching more of the Catacombs and the hidden Precursors.
Through his Spargus Monks, Veger was eager to turn on the planetary defense grid for the others, but everyone denied his offer and trusted Jak with that, instead.
Suddenly (and somehow...), Ashelin terminated Veger's privileges by dissolving his City Council. Hmmmm... I wonder why she couldn't have done that before he banished Jak to the Wastelands...
...ANYWAY! Vegean swore revenge for this.
After that recent KG assault, Ashelin knew that the KG War Factory had to be taken down NOW. First, according to Onin, Jak must find a junction box in the sewer to open Haven's old Power Room. Once that Power Room is open, one can go inside and search for a door cypher that can let them unlock the factory's gates.
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So here's the third and last sewer mission. You can find yet another way into it somewhere within North City.
There are more KG bots here, but some of them move and behave like Metal Heads. They must be adapting to their partners-in-crime.
At one point, you open a gate that triggers and automatic cutscene of Jak & Daxter sliding down through. At the end, Daxter smacks his face right in the water. Silly little Ottsel...
Be sure you check any alternate paths along the way through this section of the sewer, too. You might end up encountering room with free Precursor Orbs.
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The end of this sewer path will be the junction box to unlock the Power Room's door, and then the exit will bring you just about right in front of that Power Room.