Desolation
From Halopedia, the Halo wiki
Tombstone along with Desolation are upcoming maps for Halo 2. They are remakes of Hang 'Em High and Derelict.
By it's appearnce it is safe to say it is on Delta Halo, because the design of the buildings is not the same as human. And it also appears to be the same kind of architecture as the Campaign structures on Delta Halo.
Like it's precurser, Derelict, it probably features the same weapons. Save for the fact the Assault Rifle spawn is probably replaced with a Battle Rifle or maybe even an SMG.
