Is Summoner Skirmish considered Low or Medium OPL?

Ruling: Summoner Skirmishes are Competitive High OPL. There is no "medium" OPL category - only Low, Competitive High, and Professional High.

Nuances:

• Competitive High is the default competitive rules level
• Professional High is used for especially serious events (like top cuts at regionals and events above regional level) where rules infractions get upgraded easier and there are higher expectations such as players having to shuffle each other's decks before each game
• Summoner Skirmishes and regional Swiss rounds use Competitive High OPL