I search for solutions in this order: Past Code, Unreal Source, Wiki, BUF, groups.yahoo, google, screaming at monitor. – RegularX

From Unreal Wiki, The Unreal Engine Documentation Site

This actor, when triggered by a player, causes his view to gradually fade out into darkness. There are only two places where this actor is known to have been used:

• The end of the CityIntro.unr map that starts when Unreal Tournament loads.
• The end of each map in the Operation: Na Pali demo (a project to make a second Unreal Mission Pack). (Note: In the final Operation: Na Pali version (1.2), it is no longer used, instead being replaced with a "fadeoutteleporter").

This actor is primarily of cinematic use in Unreal Tournament. Few mappers will have the need to use it, but it is still an interesting thing for them to know.