Stormwind Assassin's Guild

Stormwind Assassin's Guild (or the Stormwind Assassins' Guild and simply the Assassins' Guild) is a group of assassins operating in Stormwind City. Mathias Shaw is either a member or its leader.

Members

 * Daerion the Assassin, sent by Katrana Prestor to kill Lo'Gosh, but failed.

Speculation
It is currently unknown whether the guild is another name for 7, or its subgroup or another group.

Before the de-canonization of the RPG books, given the fact that the guild operated in Stormwind, it is possible that both, the item and the comic mentions of the guild were originally meant to refer to the Stormwind Assassins which was apparently meant to be the background for the SI:7.

Alternatively, it could be an alternate name for the Assassin's League or its subgroup.

As per the words of Sean Copeland, unofficially, they appear to be a separate group from SI:7, but there might be some interplay between the two groups.