Only one Octolith left now, so we'll head for the Vesper Defense Outpost.
Exit your ship upon landing and break out your map. See the red door at the far end of the Weapons Complex? That's where you need to be. Take the teleporter nearby for a short cut, but don't be surprised if a hunter ambushes you upon arrival. Use the Imperialist to break through the red door, beyond here lies the Stasis Bunker - home of a family of Guardians in stasis watching over not one, but two artifacts.
The door will seal behind you, so you're not going anywhere until recovering those two artifacts. Explore the area to discover VDO Cartograph Artifact 02 and VDO Attameter Artifact 02. You'll also be able to pick up UA Expansion VD.02 here as well (it should be your final one, you should now have a maximum of 400 rounds).
With both artifacts secured and all hostiles taken care of, look for a number of scan entries around the upper stasis chamber for your Logbook before leaving, including Seal Sphere 03, 04, Oubliette 02, 03, 04, 05, 06 and 07 (lots to learn here).
Exit the chamber via the upper door near the Stronghold Portal to continue your search for the very last artifact in the game. Beyond lies a tall elevator shaft with a grand view of outside space. Wait for the lift to descend then hop aboard and ride it to the top. At the apex of the shaft you'll discover an inactive ship deck teleporter, scan the switch to fire it up and return to your ship for a quick save.
Return to the Ascension shaft and proceed on. Beyond here is the final unexplored region of Vesper, a gigantic silo known as the Fuel Stack. As you step inside you'll witness some unstable debris falling down into the shaft below before a warning appears alerting you to the danger of the now-overloading systems. You've now got 1 minute to get yourself to the top of the shaft where a lone terminal lives and your only chance to shut the overload down.
Running out of time forfeits a life, so simply reload your last save if you want a perfect record. VDO Binary Subscripture Artifact 02 awaits you here, check the Artifact Locations guide for tips to make it to the top of the shaft in under a minute (really, why couldn't they just have the shutoff terminal beside the door?).
With our favourite bounty hunter's life saved and the absolute final artifact secured, time to go get that eighth Octolith. Before leaving the Fuel Stack be sure to pick up Missile VD.02 and look for scan entries for Cooling Vent, Alimbic War 08, Silo Levitator, Methane Pipeline, Seal Sphere 02, Alimbic Order 05 and Cryogenic Storage.
Once you're ready exit the Fuel Stack and take a trip back to your ship to save the game. Return to the Stasis Bunker and step inside the Stronghold Portal near the upper door. Cross the hallway in the void and enter the Octolith's chamber to face the final Slench defense drone. Refer to the bosses guide to send this one back to the assembly line with all the others.
Conquer the final Slench to lay your eyes on the final Octolith in the game. Well done! "Alinos holds the key to ultimate power..." Now we're getting somewhere. Grab any health refills before you leave (you'll definitely need them).
On this final escape sequence you've got a measly 3 minutes to get clear. So let's not waste any time. Quickly return to the VDO and ignore the civilisation of enemies the Stasis Bunker throws at you. Run for the exit and dash back to the Weapons Complex.
In here a hunter or lone Guardian will give you trouble, quickly dispatch them and ignore the annoying Psycho Bits. Don't waste any time in the Bioweaponry Lab, just run for the VDO Gateway. Once inside use a jump pad to reach your ship faster if you want, just be certain not to accidentally fall into one of the teleporters.
With you safely back in the warm cockpit of your ship, take off and head for Alinos. Upon landfall make your way to the High Ground region and don't let any hunters stop you. Exit the area via the door behind the artifact's empty pod and head for the Combat Hall.
You'll no doubt face competition here, conquer your challenger and move on to the Alimbic Cannon Control Room. Now for some action. Step into the blue light in the center of the chamber and watch as all eight Octoliths emerge and power up the enormous Alimbic Cannon somewhere outside.
The cannon will promptly beam a signal into open space, upon which the very fabric of space tears open, revealing a huge organic structure hovering within a distorted timefield. Your gunship will chime in and alert you to this phenomenon as well. With your task complete here, return to your gunship and leave the planet (don't be surprised if hunters or the odd Guardian still pester you along the way).