Instructions
Set your character up for offense by equipping your fastest weapon, as well as armor that raises your damage output or agility. Defensive statistics are negligible in this fight; Blangonga strikes fast and hard, making avoidance your best option.
Equip the fire shield and a fire-enhanced sword. Blangonga is weak to fire, and only a fire sword can break his fangs.
Place a stun trap before you attack, then get Blangonga's attention with an arrow or by running past him. Lead him into the stun trap and start an all-out assault, doing as much damage as you can before the stun breaks.
Attack Blangonga's head to break his fang. Breaking his fang disables the roar ability that he uses to bring additional monsters into the fight.
Wait for Blangonga to attack you. After each attack, Blangonga will pause momentarily while he readies his next barrage. Dodge the initial attack, and hit Blangonga in the legs and face while he is regrouping.
Follow Blangonga into his den once he tries to limp away. There you can kill him with relatively little struggle, since he will by now be weak from the fight.