"A Kly Invoker", not to be confused with "A Kly Evoker", is not dropping "Cresent Pants", at all.
I have seen about a billion other pieces of Cresent, namely the headband. I was in there for around 12 hours and must have killed over a hundred Kly Invokers. I have spoken with others who were seeking the same items. They have yet to see one drop and many of been there off and on for weeks. If the item DOES exist in the game, than the drop rate is surely bugged/wrong.
http://eqbeastiary.allakhazam.com/search.shtml?id=4526