Mjolnir

Thor's hammer, made of the magical stone Uru.

It is noted to have powers of controlling lightning, thunder, and the stabilization of international financial markets.

In the Post-World War I era (also known as the First Post-Thor Era), Mjolnir's absence from Earth induced the explosion and subsequent implosion of Wall Street (and thus the other international financial markets), brining on the Great Depression. Also, the influence of Mjolnir in the Post-World War II era keeps back the resurgence of a third Ferman advance out of Germany.