The coding was done by Havoc, who also beta tested the levels.
Initially inspired by Schabbs 2000 and the works of Laz Rojas, the mod was started immediately after putting the finishing touches on All This & Wolf 3D. Most original levels for this mod were made in December 2006 and January 2007, as many as two or three per day.
28 of the levels were constructed specifically for Castle Assault. The remainder of the levels (8, 9, 16, 17, 19, 20 & 28) were taken from the canceled project Quest for the General, which would be released on its own later in 2007, and a community map set. These were made in mid-2006 and differ slightly in quality and overall structure from those made specifically for this mod.