Marvel confirms that Thor is actually the God of [SPOILER], not thunder.

A team of heroes known as the Defenders were brought together by Doctor Strange's sorcery to defend the universe from the time-traveling bad guy Carlo Zota.

The gang goes back in time to the earlier iterations of the Multiverse to do it. In truth, the foundation of Marvel's cosmology is the idea of cyclical destruction and rebirth,

 according to which each manifestation of the Multiverse (or "cosmos") is doomed to be destroyed by some disaster and subsequently resurrected in a different but comparable form. 

The Defenders' voyage takes them back to the Fourth Cosmos in issue #4 of the series, which includes the archetypal concepts that are reflected in the present cosmos 

(the Eighth) in the shape of heroes and villains engaged in never-ending conflict.

Ewing and Rodriguez identify all the archetypes that occurred in the Fourth Cosmos in Defenders: Beyond #2 and explain how heroes and villains are descended from each one.

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