Supergirl Annual #2 (2010)

In a special story that has direct ties to the regular monthly SUPERGIRL series, the Girl of Steel visits The Legion of Super-Heroes on Halloween in the 30th century! But Halloween proves to be just as spooky a holiday a thousand years from now as it is today, because a horrible new threat has awoken thanks to Supergirl's arrival. That horrible new threat's name is - Satan Girl! Brainiac 5 has a plan, but it may come at the cost of shattering his potential romance with Supergirl! -- dccomics.com