The obvious choice is the provincial rival, the Calgary Dragons, but there are a few other rivals I can think of during my time as a member of the Edmonton Blizzard. Late season 20, early 30's it was the New England Wolfpack punishing us in back to back finals matchups with an 8-1 record, ultimately ending what could have been a dynasty and becoming one themselves in the process. STHS even marked the two teams as rivals during that time haha. Mid to late 30's the Blizzard went in to hibernating as they rebuilt their roster and while they didn't necessarily have a rival the Hamilton Steelhawks also entered a rebuild of their own at the same time so there were always comparisons. That rivalry went away in the early S40's, but was rekindled in the late 40's to early 50's as the Steelhawks spoiled what could have been another dynasty opportunity with a pair of finals eliminations of their own. That being said I believe the Steelhawks would be considered the Blizzards biggest rival right now.