Travelling to Meridian can be quite the journey and it will always be good to do some quests, clear some Bandit Camps, clear the Corrupted Zones and maybe explore the world a bit because when you get to Meridian, there will be a plethora of new quests waiting for you there.
Upon arriving at Meridian you will gain access to the Golden Fast Travel Pack. Beyond this point in the game there will be a lot of quests and you will need a lot of Fast Travel Packs to get around the map. Golden Fast Travel Pack will greatly aid you in your journey and it is highly recommended to acquire this before continuing on.
Follow your quest marker all the way to Meridian, the City of Sun. When you are close, cross the long bridge all the way to the gates of Meridian and speak to the Checkpoint Commander. This will start a cut-scene with Erend and a new quest.
At the Checkpoint Commander, Erend will come out to greet Aloy. Talk to him and follow him to Olin's Apartment and to discuss further about Olin.
Once you reach Olin's apartment, Erend will kick down the door and you may now use your Focus to scan the area for any clues. Check the rug for anything suspicious.
Go up the stairs to continue your investigation and climb up the ladder to find a stack of Ingots. Use it to smash open Olin's secret workshop and investigate the workshop.
Scan the workshop with the Focus to reveal information about Olin and his whereabouts. Erend will talk to you about his sister and offer you a quest to investigate her death. Now its time to look for Olin at the excavation site.
Follow the quest marker to the excavation site and enter the area. Upon entering, a cut-scene will start and a mysterious voice will introduce itself to you. Entering the excavation site will also start the battle.
You must kill the Corruptors and cultists. Stealth kill the cultists before climbing down. Corruptors are weak against fire damage. Use the boulders for cover against their missiles. Once you've killed all your enemies you must talk to Olin to decide his fate.
