People are using the glitch to have their ranged classes completely avoid damage and to not deal with the additional monsters during the second phase of the Psycheflayer battle.

A tree on the right has a branch that's climbable. Some groups have people jump onto it and from there just let the healer get hate from the normal cures so that everything sans the boss targets them. But then the adds can't hit the healer, so they just walk and target the wall. The height difference also prevents AOE damage on the healer and/or BLM.

Time: Saturday, September 7th, around 3:00 PDT? (Don't remember the exact time, but the day is right)
Frequency: Always possible?
World name: Duty Finder
Character name: Cyril Elyon
Race: Elezen F
NPC name: None
Monster name: Psycheflayer and Marionettes.
Class/Level: 50 WHM
Party or solo: Party
In-game time: Unknown.
Area and coordinates: Amdapor Keep
Steps:
1. Get to Psycheflayer.
2. Run over to the tree on the right.
3. Jump up the branch (it's picky, but possible), move towards the end of the long branch. Requires another jump once you're already on the lower part of the branch.
4. Fight boss.

ISP: Surewest
Type of Internet Connection: DSL