Your only choice on the map now is to go to the desert. Your mission is "talk to sig".
First, there's a race. Learn the jumps and always have a boost in the queue so you're ready when you approach one. Finally you get the holo cube and are now on a timer to get back to the base. They're very happy with you. You earn new secrets. Sig says he'll meet you at the metalhead desert nest.
Now you're on a mission in a tunnel. Just drive quickly and blast away as you go. Little Halo-Flood guys are keeping you company in here. Soon you get a counter of 5 millipede things. Note that looking behind you shoots behind you. Just go to the green dots shooting the millipedes.
When you kill them all, you ride back to town and have new secrets. Now you have to drive to the fist icon.
It's time to go artifact hunting. Your pal says he'll drive, you just shoot. The onscreen arrows point out where to shoot. Be sure to aim for the purple balls, then kill the creatures. The last one you kill drops the artifact.
When you get back, you meet up with the ruler. He says that sand and water are like fate. He also tells you that he lost his son. He wants you to hunt down marauders. This is just a massive fight, blow them away to win. You get the Beam Generator when you do. Now you're told to go to the outpost.
Drive to the new icon on the map. Again, slay tons of people, there is no special technique needed here. Finally the door opens and four vehicles drive off. "You've got to catch them, Jak!"
Hop into your car with a timer running. Just run straight, no jumps needed. Note if you restart that the restart run is easier since you're in your car. Once you get three of them, the 4th isn't on a set timer although you can't just give up and do something else now.
When you are done, time to go back to the shuttle.
Jak and Daxter 3 Walkthrough