make a variable called "PlayerLife" or something along those lines.
Start it out at 3.
Enemies would be 'On Enemy Touch' events, set with a move route to hunt down the player (or if you want to get more clever you can custom move routes)
Enemy event code should be an animation to play on the character, and subtracting 1 from "PlayerLife"
then, so that the player will have a chance to get away before the monster kills them, add a self-switch line, and turn on self-switch A. (self-switches are switches that ONLY EXIST for the Event they are called from
)
make a new page with the same monster graphic, but as a parallel process event.
code should be wait 40 (or however many frames you want the monster to stop moving, could be more or less based on difficulty if you wanted) and then turn off self-switch A.