Originally released in 2002, "Xariim" is my solo scenario for Marathon Rubicon. 14 solo levels, one solo carnage level, three Read Me's. The (positive) review on archives.bungie.org is still up - read it if you want.
Tested with Rubicon X and Aleph One 1.2.1. Select the scenario file under Environment.
ADRESSING THE 2/5 REVIEW BELOW: Yes, it is true that this release has issues. While I don't know what the reviewer is refering to with Ataraxia being "unbeatable" (I just played through the entire package), it is true that a switch in "Closed Quarters BOB Combat" should actually be a destructable surface. As a result you can block your own progress by hitting the "switch" again. There are more similar bugs in later levels. There are other minor problems too, like some polys not having ambient sounds. That all being said, I can assure the reviewer that Rubicon Xariim was tested a lot, by me, Jane Davison and partially Christopher Lund. John Sumner vidmastered the whole thing, so you can watch him beat the Ataraxia level. The reason why these issues never got fixed is that I released the package in 2002 when I finished school. After that I was off doing the mandatory military service in Germany, so not much mapmaking going on during that time.