The Tri-geon is a special Ran-geon divided into three branches, with Transition floors connecting the branches. Unlike the Neo-geon, the starting Monster Level is based on your character's stats, so the stronger you are, the higher the initial level will be. This makes it easier to start gaining EXP in the Tri-geon. Also unlike the Neo-geon, gates do not change in level, but can rarely have the same effects as a higher-level gate. Warp gates do not appear in any branch of the Tri-geon.
The Normal branch floor themes match the Neo-geon, including the boss floors. Judgement gates do not appear, but all other gates can.
When you are in the Normal branch, the "N" will be lit on the bottom right of the screen.
The Chaos branch contains noticeably more dangerous enemies and traps, making it tougher to survive, but Exits are more likely to appear in the Chaos branch. Angel gates do not appear in Chaos, and when a Judgement, Hell or Devil gate transforms to an Angel gate, the player will remain in the Chaos branch. When transitioning from Chaos, the possible gates may lead to any of the three branches.
When you are in the Chaos branch, the "C" will be lit on the bottom right of the screen.
The Heaven branch has much less threatening enemies, including lots of Poles (which drop more coins than most foes), and most Heaven floors have a large number of chests guaranteed to have items. However, Quake Traps also frequently appear, and chests will not yield items if broken open by a source of damage other than you, the player. Care must be taken not to step on a Quake Trap when chests are within range, as the shock will break them without yielding any items. It is difficult to remain in Heaven as the Angel and Gambling gates will never appear, and the Devil and Hell gates will always exit into the Chaos branch. To stay in Heaven, the player must have a gate transform into either an Angel gate or an Abysmal gate. The transition "bridge" from Heaven is always between Heaven and Chaos.
When you are in the Heaven branch, the "H" will be lit on the bottom right of the screen.
The Transition floor between branches is accessed using a Transition gate. These areas are populated entirely by Mimics, Eyes and (at higher floors) Immortals. The Transition areas tend to have a large number of Immortal, Mine and Curse traps, with the dark floor making Mine traps difficult to spot. Each Transition floor has two exits, typically one exit will return to the branch you came from, but in some cases both a Hell and Devil gate may spawn, both leading to the Chaos branch.
When you are in a Transition area, the "bridges" between the area(s) that an exit may appear to will be lit on the bottom right of the screen.