How you didn't a screenshot, and I probably misunderstanding your questions, I'll try to talk about the hack and slash game style (Final Fighter, Excalibur, Battletoads, Ninja Turtles, etc).
You will can figure it out easy, the main issue is handle the Z order of your canvas, where an enemy from behind of the scene will walk to the front and if an ambush is between this path, you'll have to handle it manually, one by one, each object of the canvas =(
So, I don't want to teach you here how to reproduce the solution, but I already did on a old test.
Think about a shadow, place it on the character bottom, so, make your character stand for the shadow, and handle the shadow to the 8 directions. Restrict the scenario for the shadow only stay in a certain area, and when the player or monster go up, resize it to smaller, giving the right aspect of going far. When the monster or player jump, make him jump relative to this shadow, so, the Z origin of all the other sprites will be the shadow Y.
To make the monster face the player, just get the variable X and Y of the player (or his shadow), if the monster X is bigger than the X player, he is on the right, if his Y is bigger, so, he is behind the player.