This is now a series of long battles without much break. Be prepared.
Start by going along the gas pipes, avoiding the green gas. Fight your way through enemies to a waterfall area. Hop across a few more green gas-spots. Go down to a square platform that rides along. Hop the lasers as you pass them. Go into a laser-blocked room and shoot the red flying enemies. When you kill them, the laser opens. Keep moving along shooting to get you through each area. Jump the beam on the next platform, then jump the waves of fire. It's a bit like jumprope.
Go down to the water and start shooting the onslaught. Now jump into the water and swim by pressing and holding circle. Swim under the barrier. On the other side, ground pound the spot - this opens the doors and lets in the monsters. Slay them and move along. You now end up in a maze with floating platforms. There are indestructable red things to avoid. Work your way around into the center and ground pound. That opens the outer door.
Work your way out to the door. You end up in a big pipe room, shoot the enemies. Get to the silver door - you now watch a cut scene. You ride the elevator up, and hear "You're behind enemy lines". You task is to take out a cache of dark eco. Note that you can rack up a ton of gems in her if you want.
Use your board to move around. Your aim is to destroy the purple thing in person (i.e. physically standing next to it) in the middle of the area. You can ride the vines to get there. There are five of these things total, and you have a counter to tell you how many are left. The purple things are all in order and shown on the map.
When you bash the first one, the puff beast blows you to the next area. While you're grinding the vines, note that some vines have electrical spots to jump over. Falling off only sends you to the last one destroyed.
While you're grinding, it's often easier to stop on each 'island' to reset and prepare for your next run. In general, this whole area takes patience. If you get on the side ledges, note that the side tentacle creatures can be hit and hurt.
The second pillar involves two poofy things to use to get to the top. Moving on, now you have lots of poofy hops back and forth. Destroy it.
Now you have 1 counter left. Hop from mushroom to mushroom across the floor. Go slowly and turn the views appropriately. This whole level is about patience and planning. When you reach it, go up and kill it.
You've only got only one left on the grond now. There is no counter. Kill it - you are hurt. You're told to use R1 to charge and release doark strike - do it to open up the door. Next you're told to go seek out more dark eco.
"kill dark plants in forest"
Now you're in an area with green and puple spots. Use your hoverboard to ride over the green spots first, and then while trailing green streamers drive over the purple spots to squash them. An on screen counter keeps track of your progress. Really this part is not very challenging - just follow the map. You need patience to roam around looking for them all.
The circle key does the stompy shock wave, this is good to use. When you get near the end of your task, you get a 'remaining' countdown. Finally when you are done, platforms rise in the water. Go stand in the light. You get shoulder armor!
Jak and Daxter 3 Walkthrough