Moon Knight is a masked vigilante who was given a little supernatural assistance by an Egyptian God. Gazillion is selling the Moon Knight in a hero pack with two costumes and other assorted goodies.
Marvel Heroes is also throwing a combined Carnival and Mardi Gras celebration in the game. Players will get a daily gift for logging in, discover themed drops, and have the chance to buy Halloween items and costumes on sale.
[Thanks to Spacejesus3k for the tip!]