Okay, so here's the deal. You can only advance your progress with the quest once every 5 minutes.
You have to talk to the NPC from behind while your costume buff is on (either from Festive Moogle once every 5 minutes or from Skeleton Robe from event). If you talk to it from the front or without the costume buff, it will depop.
The best strategy when you find it is to pop your buff, talk to it, and then move away a little bit and wait the 5 minutes cooldown. That way others know you're waiting and can locate the NPC. If people work together, this is much less of a PITA.
So far, the advancement of text appears to be:
Quote:
You've joined the procession.
You can't stop now. You've just started!
You've only just begun.
There's still a long way to go.
Hope you didn't make any other plans, you're not even close to being finished.
Almost halfway.
It's still a little too early to go back.
Leave the procession now and someone might be peeved.
Just a little longer...
You're almost done!
Alright! It's time to collect your reward!
It takes about an hour or so to do each city. Yeah, gross.
NPCs:
Sandy - Poseaulloie
Windy - Bikho Ronpotteh
Bastok - Selma
Rewards:
1st City - Coven Hat
2nd City - Novennial Coat
3rd City - Novennial Hose
Additional Notes:
-Once you zone after beginning the quest, you lose progress. That means you can only get the first quest advancement using the festival moogle without using the skeleton robe.