You just really need superspeed & spears, nothing else.
1) trow a spear till he starts chasing you and run in circles around the room until he stops, you will notice u done it rigth if he doesnt move again no matter what u do.
2) position yourself on his back at some middle distance and aim to the rigth spot, if u hit the spot he will roar in anger :P
lol 25 spears? if you aim rigth takes only 5 or so.