It might not look like it, but you can land in the mirror if you jump off and push forward.
With Haste and Feather Fall, stand on the steps as close to the center of the platform as possible on the left hand side.
Break the explosive barrels of The Good Stuff as you go, which will cause a number of Dream Crawlers to spawn. The right-hand (west) room in the hall contains the Blue Key in a lockbox, guarded by dream creatures. Defeat the Skeleton in Jeets' Closet for a chest. This room contains a locked door opened by the Skeleton Key obtained in the previous step. Once Galamesh is defeated, talk to Jeets to end his treasure fantasy. The fight at the end is with Galamesh and a number of dream creatures varying by how many Dreamy Treasures you obtained. The air jets along the path can be turned off by pulling the levers or by disabling nearby trap Control panels. A popular strategy is to block Jeets's path at the gates with 4+ party members while 1-2 members race ahead.
There is also a skeleton key behind the second chest, which will be there even if Jeets gets to the chest first. The goal of the race is to loot as many of the three chests in the cavern before Jeets does - each Dreamy Treasure you collect reduces the number of trash mobs that spawn at the end. Talking to him will start a race down a cavern with spikes raining from the ceiling and air jets blowing you into spikes on the walls/floor. Jeets will be waiting for you just inside. This room contains a Locked door that can only be opened with the Gold key obtained in the previous step. Without Dimension Door, you won't be able to return via: East (bottles) back, later on. Only someone with Dimension Door and someone to pick/knock the door really need to do this part. The Gold key is behind the bar in this room - grab it and Dimension Door out before spiders spawn. The left door is locked and needs to be picked or knocked. Avoid breaking the barrels of The Good Stuff, which will release Dream Crawlers, and proceed through the hallway to the left (east) door. Go through East (bottles) mirror front.Walk towards Jeets and kill the Dream Crawlers. The West door has coins in front of it and leads to the treasure fantasy.The South door has steam in front of it and leads to the spa fantasy.The East door has bottles in front of it and leads to the tavern fantasy.The North door is the entry to the quest and doubles as the end-fight door at the end of the quest.If you don't, you can skip steps 1 and 2, losing out on the optional experience and chest from the Greed Monster. This is only possible if you have access to the Dimension Door spell and a way to unlock a door (Tip: Level 11 Fighter hireling, Mikayl the Pious, has Lesser Dragonmark of Passage, Spell-Like Ability: Dimension Door). The layout of this walkthrough ensures that every part can be completed. Once the objective available through the front entrance to a mirror is completed, the mirror deactivates and neither the front nor the back of the mirror is accessible. The mirrors have two sides (front and back). There is a central platform with four exits, three of which have mirrors. Some Rockfall, Air-jet traps in the "treasure fantasy" cavern area.Eliminate the last inner desire that's keeping Jeets trapped.Spoiler Warning: Information below this point can be considered spoiler material!