Red Tar

Red Tar is a corrosive biological secretion. It is black, red, and gray and will slowly eat through just about anything if given enough time.

Jack Smack, Crellit Kard, and Cassidy Tulofong are part of an unnamed alien race that secrete this mixture.

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Relevant articles:

http://squackle.com/25325/stories/they-would-deny-it-was-ground-zero/