Gundam Deathscythe (or Gundam 02) was one of the 5 gundams sent to Earth in Operation Meteor. Piloted by Duo Maxwell, Deathscythe was on a mission to destroy OZ. The original Deathscythe was destroyed when Trowa Barton (a fellow Gundam Pilot of his) was forced to destroy it when he was sneaking in to OZ's lunar base. The Gundam Scientists worked on rebuilding the Gundams, and so Deathscythe Hell was born. Hell proved to be a valuable asset. It aided the other four Gundam Pilots in destroying OZ. However, OZ destroyed itself, with the production of Mobile Dolls, OZ was split. Hell later fought against Gundam Epyon, the 6th Gundam piloted by Milliardo Peacecraft (Zechs Marquise). In Gundam Wing: Endless Waltz, DH was redesigned and made into... well... the skin being posted. DHC (Deathscythe Hell Custom) fought against the Mariemaia Army, meanwhile still being piloted by Duo.

Source:http://gundam.wikia.com/wiki/XXXG-01D2_Gundam_Deathscythe_Hell