GM (Game Master) is a player in a this game who acts as organizer, arbitrator, and officiant in rules situations.
GM in YU-GI-OH Online doing the same thing like other online game normally they don’t duel or chat with player but there is one time player can duel with GM in GM Event during first beta test.
GM Event : GM Event is Special event that let player have a chance to duel with GM on Japanese Lobby.This event appear once during First Beta Test, If you win against GM you can open special pack with special cards on it if you lose you can open special loser’s pack also.
GM Event Packs (Split by Winner and Loser Pack)
GM Winner’s Pack
Dark Magician Girl
Witch of The Black Forest
Magician of Faith
GM Loser’s Pack
Black Skull Dragon
Ring of Destruction
Credit From : http://www.geocities.jp/yugionline2/betacard.html
This game isn’t forbidden to use GM in front of your name so there are a lot of player with GM name such as GMJakarade, GMChaosEmperor, GMKevin but real GM will have something different from player for Example GM have 99 Level while player have only 30 LV maximum
When this game upgrade to YU-GI-OH Online Duel Evolution you will not see them much, sometime they appear when nobody in lobby and a lot of time they appear on Japanese Lobby.Player can’t duel or chat with GM and GM don’t chat with player too.
Some Pictures of GM for someone who want to see it
Credit Pics : Command Knight’s, GMFriends’s, hamankarn’s, Silver Cat’s, Tekachu’s Blog
Well Known GM is GMLeo because a lot of player got D-Mail warning from him about RMT, Trade Win, etc…
Credit : [SMoG]ike111 from YU-GI-OH Fande Forum
YU-GI-OH Online have 12 GM their name divide by Zodiac name you can call them Zodiac GM.
Credit : Command Knight’s Blog
I am not sure about only 12 GM in this game. in the past I think I see GM without Zodiac name but can’t remember.
YU-GI-OH Online Duel Evolution have GM Pack picture inside data of this game and There are some packs look similar to GM Packs but different color.
Maybe in the future this pack will appear again in other form.
GM’s will never ask you for your passwords or personal details so don’t believe E-mail or D-mail/Private Chat that claim his/her is GM and ask your personal detail.