The procedure is like this for EACH and every cactaur: you approach the big stone and read the riddle, you then search for cactaur, when you find it you have to play a game with him approaching from behind when it doesn't look, when you do that, you fight him. If succsessfull in all that, you'll get the cactaur's sphere with his name on it, if not, you'll get a looser sphere. Anyway, you bring the sphere you have obtained back to the stone and insert it. It gives you a new riddle. You need 10 spheres. The looser and "winner" spheres only affect the prize in the second treasure chest inside the cactaur city, you'll get the sigil anyway.
