If you had an obsidian mirror to summon spirits, what would you actually use it for?

I would like to discuss philosophy and metaphysical concepts.

But on the topic, I urge a visit to central Oregon. There is an obsidian lava flow you can walk to. Very rare. The “locals” (Native Americans as it’s said) knew about it and cherished it. It provided excellent arrowheads and blades. It was the superweapon of the time. An excellent trade good, but you only traded the obsidian to the neighbors you trusted.

It would likely meet my sledgehammer.