Halloween Cookie
From Ephinea PSO Wiki
Halloween Cookies are an event currency that drop during the Halloween event. They drop at a rate of 1/2,000 across all enemies and difficulties, excluding boxes and scared rappies. Each cookie can be exchanged to buy a party admission to one run of a Halloween quest.
Note that all Halloween quests have fixed rates of +200% Experience, +50% Drop Anything Rate, +50% Rare Drop Rate & +100% Rare Enemy Rate; so they do not stack with any other boosts.