Pit materials Obducite and Ingolith

[⚜ Maître de Bredouille ⚜]

So I visited the Pit to tier 20 and I can`t find Ingolith any more, only Obducite...

I know that these materials can only be used for tempered items, but for what items exactly?

Is ingolith for weapons only? Because I found some at the beginning (must be from the Pit, I think), upgraded a scythe and currently I have no use for Obducite...and it seems I can`t exchange it at the Alchemist. Must be lower-class material...