The Order of the Ethereal Blade was founded in the fifth century (YK) as a duelist’s society, where members of other circles could test their skills and spells in battle with fellow mages. What began as a mystical fight club became the core of the original Knights Arcane. Today, the Ethereal Blade focuses on the study and development of war magic, but it remains a dueling society whose members are always ready to prove their mettle in battle. Many of Aundair’s finest warmages are members of the Order, along with officers of the Knights Arcane and Knights Phantom.
While it began as a wizard’s circle, today the Order of the Ethereal Blade welcomes Eldritch Knights, Arcane Tricksters and others who blend martial and mystical techniques. With that said, it’s still an arcane order. There are other societies that cater purely to duelists and wandslingers, including Fairhaven’s League of ir’Lain and the Darkwood Wands of Passage.
Source: http://keith-baker.com/ifaq-wizard-circles/