This was a Legions Imperialis Diorama at Warhammer World. I took some more photographs of the diorama on my last visit to there.
Ceres City changed hands nine times during the campaign for control of the Delta-Garmon system, and the diorama captures the Blood Angels and the Titans of Legio Solaria waging war against the Iron Warriors and Legio Fureans.
More photographs of the diorama.