Little woona is a 1-1

@Call_Me_Cyber_Dash  
That explains it.

@Pilot Solaris
 
Well…  
Party Cannon  
CONGRATULATIONS, YOU DISCOVERED THE SMALL FAIL PUT THERE BY PURPO-  
Ok it depends. Legendary, yeah, but having this as a standard card…  
OkIforgotitareyouhappynow?

@PonyPon  
9/4 is an absolutely terrible statline. CoreHound is 9/5 and not played ever in the exception of very fringe decks at Rank 20. (The lowest)  
Blackhand is a 8/4 legendary, he’s considered a dead card and a waste of space unless you can benefits from his Battlecry. Once his battlecry has been used, he isnt expected to live until you can attack.
 
As for other questions:  
Yes, there is already a hearthstone card (Raging Worgen) with Enrage: Gain +1 Attack and Windfury. he gets a second attack the moment he gets damaged, so the second stealth would become useless. Also, transform effects in Hearthstone are permanent, while enrage effects can be countered by healing the target back up.
 
A better way for this card’s effect to be used would be:  
“Enrage: Gain the power of Nightmare Moon, gaining Windfury and +1/+1.”  
Or, in a more drastic way:  
“When damaged, turn into Nightmare Moon.” (Which would be a 5/10 with Windfury and the Deathrattle effect)
 
The second one is a more powerful because if she manage to transform and then silenced, she would lose windfury but keeps the 5/10.

Wouldn’t she be a Legendary?

“I’m going to turn into Nightmare Moon!”
 
“Quiet, sister.”
 
And then nothing happened.

@Call_Me_Cyber_Dash
 
I could see it as being useful for conserving the next hit, guaranteeing 3 hits rather than chancing it for 4 and hoping the enemy doesn’t have any removal. Enrage+winfury is always nice though. Would work well in a Warrior or Shammy deck.

@Zincy
 
Yeah, the windfury allows a second attack immediatley, and no, I don’t know why…  
Maybe if you just don’t want to?

So it would enrage on attack, since its stealth and can’t be targeted…would windfury proc during that turn and allow for a second hit? What would be the point of readding stealth since you’re going to swing with it again?

@Ilsor
 
Only if by the purpose of protecting it until the right time.  
Still, why stealth AGAIN?

I’m not sure if putting “gain Stealth” in Enrage would work.

A little too much.
 
I would suggest this thing I came up with, Spelldeath where being killed with a spell triggers something, in this case, summoning Nightmare Moon.
 
With stealth and 9/4