Nexon Japan loves working with popular animes, and Fairy Tail is certainly 1 of the top series out there. Having appeared in Dungeon Fighter Online (Arad Senki) previously, Fairy Tail has now invaded Mabinogi Heroes with exclusive content and of course, cash shop costumes (look pretty weird here).
The promotion started last week, and will end in mid-July. Players of the English servers, Vindictus, apparently have not seen any of such cross-promotion before. While it certainly demands a huge licensing fee from the anime IP owners, I guess it wouldn’t harm to try 1 and see the feedback.