This type of blade also know as "Dragon & Tiger blade (龍虎刃)" as it combine the advantages of the agility of Jian (double edge straigth sword) & ferocious power of Dao.
One of a interesting story of where this unique style of blade came from was during the "Warring States Period" (476 BCE to 221 BCE) in Chinese History, a student , who learnt the art of war from his famous Master Gui Gu-Zi (鬼谷子), was about to leave his master and join the war. As this student were very good in both Jian and Dao, so Master Gui Gu-Zi personally forged this unique blade for his student as a farewell gift and named it "Dragon & Tiger Blade. Of course, it is just a story, no one knows whether this story is true or not.
In Yang style taichi, (the Yang Cheng Fu "big frame" system), there is a taichi saber which looks a bit similar to Yi Mon Dao. (see photo in below), however, it has nothing to do with authenic Yi Mon Dao and the specifications and the way to use are also compeletly different. Yang Tai Chi saber is believed to be created by Master Yang Cheng Fu, based on a Japanese Sword. and mainly used with single handed.
Yi Mon Dao, on the other hand, is a very difficult weapon to master, much longer blade and can be used in both two handed (70% of time) and single handed, and can be regarded as a most fearful weapon once mastered as the unique design allow the swordsman to attack in unexpected angles/directions with very fast speed and great power.
This particular sword was made 8 years ago. It took almost 3 months and broke quite a few blade bodies during forging & quenching before this one was eventually born. As this sword was made for real combat sword, so the steel, overall strength and balance must be taken into consideration while making this unique piece.
As the result, this blade is sharp enough to shave paper while strong enough to cut metal hair clip into half. Back in that time, this sword was one of the best you can get, and it still holds true today when comparing with most of swords you can find in the market.