All of the following custom maps require a valid, licensed copy of Unreal Tournament 2003 to play. Compatibility with Unreal Tournament 2004 does exist, but is a bit spotty, so good luck with that.
DM-Epsilon

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Third Helix
Epsilon Station is a remake of my old Unreal Tournament map DM-Champions. In addition to a significant style upgrade, DM-Epsilon features some layout differences and gameflow improvements, allowing for lots and lots of cool new tricks. This map is pure deathmatch bliss with four players, or in 2v2 games.
DM-Fate

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Third Helix
Fate was expressly designed as a 1v1 duel arena, though it features interesting play mechanics with three players. It’s small and straightforward, and duels generally turn into tense, nail-biting hunts where the kills come suddenly and without warning… that is, if you’re not paying attention.
DM-Forbidden

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Third Helix
The Forbidden Temple is an ancient structure hidden deep within the desert. It provides a wide-open deathmatch experience for 4-8 players, and some great tricks can be pulled off if you’re clever enough to use your surroundings. This map is also great fun when playing Invasion.
CTF-Arena

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Third Helix
Arena is a test concept for an arena-style team-based map. Here, I was going for the “sporting event” feel that was not strongly present in UT2003. The map itself is ridiculously simplistic, and it can be very, very hard to score with more than four players in the game. However, the ambience is very cool, so check this one out!
CTF-Elesel

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Third Helix
Elesel Wood is a fairly straightforward CTF map set in an ancient forest. Be sure to explore the far reaches of the woods thoroughly… you might find something amusing!