And the probability to attack n times is 1/(2)^n , so a chain of infinite attacks is very unlikely. Nothing to discuss here, I guess…
BUT !
Let’s do some more math because I like it 
Let’s say you cast it at turn four, so it starts attacking (IF not dealt with before) on turn five where you almost certainly dealt a mean of 3 damages to opponent’s face, (you smorky).
So he’s at 22 and you need nine extra attacks from him and one from your general
( your other creatures are dead because your opponent can’t do his math and tought that IT WASN’T SUCH A BIG THREAT AFTER ALL!! [And he was right] )
BUT!
Your opponent has some creatures, because I guess you were too busy smorking to clear board, weren’t you?
So let’s say a mean of three creatures with a mean of four health each
Another six attacks to deal with everything, and we have:
1/(2^15)=1/32768= 0,000031%
BUT!
Let’s say you want to ignore creatures and hit only the general (you smorky)
You will have to count enemies remaining and the probability to hit just one of them, times the probability NOT TO HIT THE OTHERS!
So…let’s say four total enemies
Each extra shot has a probability of [1/2][1/4][1-3/4]=1/(2^5)
For each shot
To a grand total of
[1/(2^5)^10]=0,0000000000000009 %
Conclusions:
Totally OP
Let me know if I did everything right (even with grammar, not my mothertongue)
Bye folks, when you reach the fourth turn OTK notify me