For those looking to play these today, there are two primary methods for Xbox hardware or PC:
Are you planning to play these on or through emulation ? Tomb Raider: Underworld ISO & XEX DLC - XBOX ...
“Hardcore fans will warm to Lara's Shadow in a way that they probably didn't with the rather disappointing Beneath the Ashes .” Eurogamer.net · 17 years ago For those looking to play these today, there
These DLCs are fully backward compatible and can still be purchased and played on modern Xbox consoles. Tomb Raider: Underworld ISO & XEX DLC - XBOX ...
Reviews of these expansions are mixed, often balancing the thrill of new content against its short duration.
If you're a story completionist, Lara's Shadow is the most essential piece, as it officially "ties up the ending in a nice little bow".