Revealing mistake: In the arrow contest, as Robin was about to be assassinated, Blinkin grabs the arrow. If you look closely, as his arm reaches out, you see that Blinkin already has the arrow in his hand.
Revealing mistake: When Blinkin falls out of the look-out post and crashes into the large tree, you can see it wobble.
Answer: Gibberish.
It means literally "I will send you to hell".