A huge dragon (actually a wizard) that was revived by Bowser in HTF Origins. Bowser uses him to threaten Happy Tree Kingdom, as well as to capture every resident there. Fortunately, only very few survived this monster's rampage.
The dragon's midsection is the only part of his body that can be damaged. Thus, the player has to shoot that part, all the while dodging flame shots fired by this boss. After the player defeats him, he'll explode.
You can encounter the dragon in the penultimate level in HTF Origins.