With the list of the initial post I'm getting first to third turn kills on a very regular basis. You usually drop to about 10 life, only lower if you happen to reveal an Ad Nauseam. Tendrils then hits for 20-22 minimum and went as high as 38. Often I even had a Duress a round before I started.

Apart from play errors that could have been avoided with more practice I fizzles only once because I killed myself with Ad Nauseam while not finding a single tutor for Tendrils in 25-30 cards.

The deck is also very flexible when it comes to mulligans.

Even without further testing against blue/black decks the card's power level is way to high for Legacy. I'm not whining btw, just stating how I see it.