Board Thread:Questions and Answers/@comment-5600064-20150129221510/@comment-6192846-20150129222034

Neither, technically. It's an event mentioned in passing in Epic of Evil: The Daughter of Evil Fanbook, dubbed the "Duel of Merrigod Plateau". The event itself is mentioned in passing in Evils Kingdom and Deadly Sins of Evil: Evil Food Eater Conchita.

Just for the record, when asking a question about something happening to characters, might help to check their articles (ie Elluka Clockworker and Irina Clockworker). All that's known about it is there with references to the source.