Tantalus is briefly mentioned in Axton's personal ECHO log. The unused Dahl vending machine quotes mention mercenaries on this planet holding off an Atlas armada incursion.

It is listed as Handsome Jack's home planet from the official profile infographic of Hyperion.

Profile Hyperion.jpg

From humble beginnings on the planet Tantalus to his discovery and master of Pandora's elusive vault and rise of power as head of the Hyperion Corporation, Handsome Jack has shown that where there's a will (no matter how twisted), there is a way.
— Hyperion Profile Infographic
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