Acrophobia (Phobia) (3.5e Flaw)
From D&D Wiki
Each turn that the character is more than 15 feet above the ground they must make a Will Save and it is increased by one each turn.
If they fail their save, they suffer from the following effects:
The first time they fail their check they become Shaken.
The second time they fail their check, they become Frightened.
The third time they fail their check, they become Panicked.A character that is no 15 ft. or more from a flat surface can make a DC check based off their last failed roll to remove the effects of the Phobia. They can only make this roll once every ten minutes.