In the Iki Island expansion, there is a special Horizon Forbidden West-themed armor set that can be obtained at the Forbidden Shrine. At the shrine, there is a scroll containing a poem hinting at how to do so. Spoiler:The player must equip Tadayori's armor and activate focus hearing to reveal 3 targets along the shrines statue: one above it's head, another on its hand, and the last on the head of a demon that the statue is standing on. Once completed, the corruption wrapped around the statue falls away and the player receives said armor

The corruption wrapped around the statue is a reference to all the corruption tainting the land and machines in Horizon Zero Dawn and Horizon Forbidden West.