This store used to be known as DiveDice but has recently changed their name to Rollingdice.
It is a few minutes walk from Hongik University subway station (exit 2) in Seoul.
It's a board game cafe which means it’s a lot nicer than some of the dungeons I played at in Australia. It has good lighting and toilet facilities inside.
While they have two walls absolutely stacked with board games they seemed to know their Magic and the window blinds were magic themed (I was impressed). The guy who seemed to be the owner played in and judged the event and was friendly and helpful.
There was one other staff member at the store, while I was looking at the sleeves trying to guess which were the correct size for magic he asked me “Can I help you?”
This was not only the best customer service I have ever got in a Magic shop it’s the best in Korea as most shop staff try to avoid having to speak to foreigners (understandable).
Apparently they have a couple of drafts during the week, Friday night draft and standard (starting around 7:30 pm) and tournaments Saturday and Sunday (constructed or sealed) and usually a draft after each tournament.
Rolling Dice Hongdae also have a sister store called Dive Dice Hyehwa which apparently has some issues with customer service. I have only heard good things about Rolling Dice Hongdae which match with my personal experience.
Phone number: 02-323-7455
Email address: firstname.lastname@example.org
Korean Street address: 서울특별시 마포구 동교동 200 - 29 번지 동진빌딩 3층