The Defenders #21

Beware the Black Rain!" warns the tagline on this March 1975 Marvel issue, and the cover by Gil Kane and Klaus Janson makes the threat vivid: a rain-soaked Hulk charges forward through a crowd of frenzied civilians while Doctor Strange and Valkyrie brace alongside him, the word balloons declaring that this mysterious black rain has driven an entire city to madness — and only these three Defenders stand against it. Steve Gerber scripts the interior madness, with Sal Buscema on art, making this a compelling snapshot of the team at its scrappy, outnumbered best.