This is a main mission of the game, so it's unmissable.
https://starbounder.org/Find_Clues_to_Locate_the_Hylotl_Arti...For this next Artifact you'll be tasked with scanning Hylotl objects. Ocean planets are probably your best bet, as only Hylotl underwater cities and dungeons appear on them, no other type of village or dungeons will appear. I personally got most if not all of the scanned objects needed from the first underwater Hylotl city I found. After collecting all the scans Esther will send you to the Grand Pagoda Library.
https://starbounder.org/Grand_Pagoda_LibraryLike the story dungeons before it, this is another simple job of making your way down the dungeon until you get to the boss. Koichi will appear and help you along the way. Make sure you fully explore though, as I found 6-8 codices towards the 100 total, quite a lot of them compared to the other story dungeons so far. But of course you can always come back later if you miss anything.
The boss is Asra Nox, who might seem daunting at first, as you'll notice you can't even damage her. What you need to do is dodge her patterns of attack, until she gets tried and loses her shield and lets you get some hits in on her. You then just repeat the process until she'd defeated. She'll always do her spinning ball attack right before she loses the shield. Then you grab the artifact, and you and Koichi will return to The Outpost, where you talk to Esther as usual and this unlocks.