I don't see a TM symbol anywhere and some searches of the interwebs reveals nothing but laughing cats...
I'm not wanting to infringe, just not step on toes.
(Very big, powerful toes)
It does seem that wizards has trademarked all of the guild names (list here), so I would avoid using them without express permission or a licensing agreement, as wizards could pursue legal action.
However, trademark is primarily for commercial endeavours, so if this is for personal use there shouldn't be an issue.