[treeman79]

There is also Superman’s key. Made of neutronium.

https://dcmovies.fandom.com/wiki/Fortress_Key_(All-Star_Supe...

Last I tried to calculate (poorly), if you were to touch it. You liquify and be sucked into it just before contact.

[ben_w]

(Superhero physics is vague and unrealistic at the best of times).

Assuming "dwarf star material" means "neutronium" (which is unstable at any level less than a neutron star) and the "half million tons" mass quote for the key…

That's about the energy content of all the world's fossil fuel reserves being released in a 10 minute half-life.