I'm starting to think that this is also one of the Best done Guilds. Thoughts?

I would say so as well. Mage and Fighters Guild, yo, go kill these rivals/necromancers. Arena, right round after round in the same environment. Thieves guild was also pretty good though but Dark Brotherhood had betrayal and everything around every corner. Also you had to find crafty ways to kill people.

Betrayal? Allright No more Spoilers