Elder Altar

Elder Altar is a tool for alternate crafting of Elder weapons (such as Elder Bow). You need to find its recipes by exploring Elder biomes.

Some books (codexes) in Elder biomes will contain instructions on which ingredients you need to combine. Secret area of Baron's Keep mission also has these books.

Using the Elder Altar doesn't require research or blueprints, but the components you will need are very rare. They include items like Nocxium Bar, Elder Tome, Valtan Casing, etc. Some of them require an Elder Artifact, which is only found in Delta Freya II mission.