grafikal just knows too much, that's why you say that =p
Anyway, that's simple
Make an hidden event on the floor, and make it "player touch". That event will be in the floor when you want the creature to chase you. Then, when you hit that event with your player, it turns on a switch.(ex:switcsh1)
Then, erase this event.
Go to the monster event, and make a new page, put (when this event is on[switsh1]), and make his movment "Toward Hero". And if you want him to kill you, make him event touch, and GAME OVER on the options!!!!!
W/e that's SOOOoooo hard uhhhh, you could use your imagination, and the options of the RPG MAKER. That's more than the basics...