Horizon Forbidden West: Forbidden Legacy Quest Walkthrough

gamerant.com:

There are a lot of side quests and errands in Horizon Forbidden West, and while most do a pretty good job of adding a little extra depth to the game's world, some of them can be fairly forgettable. This definitely isn't the case when it comes to the Forbidden Legacy side quest though, which is handed out by Alva towards the end of the main story.

Horizon Forbidden West: How to Override The Shining Wastes Tallneck

The quest features a little bit of everything, from combat to climbing, with a few door code-related puzzles thrown in there as well. It's also one of only ten side quests and errands that actually need to be tackled to unlock the platinum trophy for Horizon Forbidden West, with the «Recovered Alva's Data» trophy being one of several rewards that players get for completing the quest.

Players will gain access to the Forbidden Legacy side quest near the beginning of the Gemini main story mission. After speaking with Beta down in the server room, players should head back upstairs and talk to Alva. They'll need to select the «Did you need help with something?» option, which will lead to Alva telling Aloy about a lost flood control system known as Leviathan. She'll then ask for help tracking it down and Forbidden Legacy will be added to the list of side quests in the player's notebook.

To get the ball rolling, players should head on over to the Legacy's Landfall area, which is in the ruins of old San Francisco to the far west. Once there, they'll be able to call Alva from the nearby campsite, and, after a short conversation with one of the other Quen, she'll lead Aloy to some nearby ruins. Investigating the area a little will lead to a Slitherfang appearing from the sand, which players should dispatch using Fire, Frost,