User blog comment:Roboartitec/Guessing what's Merlin's sin/@comment-3544775-20130106111643/@comment-3544775-20130106125045

Well she wasn't fat 10 years ago, while she was already called with specific Sin, so I hope she is not fat now too :> - http://nanatsu-no-taizai.wikia.com/wiki/File:The_Seven_Deadly_Sins_10_years_ago.png (on the left, with the dress). It also appear that she is flying, which even more fits her name as Merlin and Wizard. And from the other pic, she appears to have a crystal ball or something (probably her magical weapon).

About her name: Second chapter around 4th or 5th page. Their posters again where shown. It revealed King, Ban and Merlin full names, but the speach bubbles covered the rest of the sins name and Gowihe/nd or something like that name is partly seen too.