-( Story related, cannot be missed )-
After the events at Tombli Outpost, Vorselon's ship will appear once more as a destination. It seems ol' Vorselon went and caught Azimuth, and will release him only if Ratchet offers up himself instead.
The main fight against Vorselon is only slightly more challenging. Whatever your strategy was for the first fight should still work, but make sure to employ all of your new weapons since then to take care of him more easily. The rest of this level is pretty explanatory (even with handy map markers that show you where you need to head to free your fellow Lombax).