Everyone likely seen footage of Labrys as the boss in Persona 4 Arena and her darker counterpart. It's has been announced that they will be added to the playable roster in the arcade version.
Regular Labrys will be available to play this Wednesday while Shadow Labrys is coming on April 19.
Fans of Persona 3 will know about one of Igor's assistant Elizabeth. She will also be playable on April 5. These characters will likely be available through NESiCA Live online updates. These are probably the first batch of many new characters to come.