Q: What does "5th level manifester" requirement of the Psychic Assassin PrC mean? If I have a psychic warrior/ninja, would I need to have five levels of psychic warrior or five levels in any class?
You need to be a 5th level manifester to qualify for this prestige class (found here), so you would need five levels of psychic warrior. Many times for psionic prestige classes we would state "must be able to manifest a 3rd level power" or something to that effect, but in this case we chose to use straight manifester level.
--Scott Brocius, Psychic Assassin Author