Explorer/Adventurer Lewis Conrad, while searching through a forgotten part of the Amazon jungle, encountered the mud-thing known as Taboo. Taboo revealed he was stranded on the Earth, and needed all of humanity's scientific knowledge in order to find a way to return to his homeworld. Conrad delivered a machine containing all such information to Taboo, who then revealed his true intentions of using the info to conquer earth. As he flew off to his planet to share the information with his race, he and the machine exploded. The scientists revealed that along with the knowledge, they also included an H-Bomb, in case their suspicions about Taboo were correct.

The explosion, however, simply blew Taboo into pieces, which then fell back to earth and merged back together. While going on a rampage through a city, Taboo's fellow aliens arrived, and took Taboo away, explaining that Taboo was mentally ill, and that their race was not warlike.

Some time afterwards, the alien Xemnu used a robot in the form of Taboo to battle the Hulk.

Taboo, or rather a larger monster resembling him, was among the monsters summoned by the Mole Man to greet Adam Warlock upon his arrival on Monster Island.