How do you beat mission 14 in spider riders

i don't know how please help me
I only managed to find corona. first talk in the map of the spiders' arena to the man. he will give to you a necklace. bring the necklace to the woman in the house (from the first map of the town go south, the first door on the left). she will give to you some money. use the money to buy the pick in the shop. then go to the forest (the maps that look like a dungeon) and collect the four flowers in it. go in the map of the aracna's doors and go right to the field. give to the woman the four flower and she will thank you. go in the village the map on the right and talk again to her. she will give to you a potion. then go south west until you find a big rock. break it with the pick and go trought in the cave/swamp until you find Corona. she is wounded so give to her the potion. she will tell you to flee. but when you try to go away a monster attack you. the monster is really strong (stats: red 16, green 20, lives 25) and I couldn't destroy him. if someone can help me, please tell me how to kill him. to beat him you have to have 4000 victory points