Magic The Gathering: House Dimir does not exist. Of course the Guildpact relies on ten guilds of all possible mana combinations, but the blue black one is just a myth. That tenth symbol on the wall showing all the guilds? Artist's license. Duskmantle, House of Secrets? Never built, don't know what you're talking about. Those mysterious spirits that the Boros legion fought last week? I don't remember that, and you don't either.