First place an NPC to be used as an enemy, I used a lion.
Make 3 pages in the lion.

On the first page have it activated by being touched by the hero.

this will be where it hurts the player

On the second have it activated by push key,
and have the conditions as a variable called LionState be 1.

this will be where the player hurts it

On the third page have the picture blank
and have it activated by anything other than AutoStart and have the condition as a switch called LionDead on.

this (obviosly) is when the lion is dead

On the 1st and 2nd pages have the movement as move toward player
(This is so the lion moves towards the player)
and the frequency at 8
and the speed at 1/2 faster.
(this speed is half the speed of the default speed for the player, i find this a good speed so the player can run away)
and the priority type as Common Char Above

for the 3rd page have it the same except random movement instead of follow player.
and the priority type as Common Char Below

next, make a new NPC called setmonsters.
make the pic blank.
set it to autostart. make 3 pages,
the 3rd page is optional if you use the 3rd page, place the NPC in a place the player can not step on, but can be acessable by the PushKey command

on the first page have it set a variable called LionHP to 20 (or what ever number you want the lion's HP to be)
then have it set the switch LionLive to on and LionDead to off and a switch called MonstersSet to on

leave the seond page blank but have the condition to the switch MonstersSet

on the 3rd page (optional) have the pic as a stone or something like that.
set the priority to Common Char Above
set the start condition to PushKey
set the conditions to the switch LionDead being on
have this page do the same thing as page one (copy, paste)

the 3rd page will restart the lion when you do the push button on it, it will only appear once the lion is dead

make a new NPC called MonsterState
have it set to Parallel Process
have it change the variable LionState to 0
wait 0.1 secs
have it change the variable LionState to 1
wait 0.1 secs

what this does is switch between the lion being activated when you attack it and when it attacks you, this is necessary because you can not have 2 pages on the same NPC run at the same time.

now, back to the lion

on page one (the one with at hero touch)
have it play the sound effect lion (or roar or another you find to sound good for the lion attacking)
have it show the battle animation claw (or a different one) over the hero
have it flash the hero for 0.4 seconds
do a set char movement for the hero, frequency 8

move speed up
move speed up
turn 180o
move forward
move forward
turn 180o
move speed down
move speed down

set ignore if cant be done

what that will do is make the character fly backwards

then do take damage for all party members
i used:
attack power 5
Defense Effect 40%
MindForce Effect 0%
variance 5

but you can use something else. the defense effect is highly recommended however, because this makes it that your armour will have some effect and for magic attacks the mindforce effect is highly recommended.

on the 2nd page (the one with push key)
play sound effect kill10 (or another one for attacking the lion)
show battle animation sword1 (or a different one) over this event (do this event for obvious reasons)
flash char this event for 0.4 seconds
do a set char movement for this event, frequency 8

set speed up
set speed up
set speed up
set speed up
turn 180o
move forward
move forward
turn 180o
set speed down
set speed down
set speed down
set speed down

set ignore if cant be done

this nocks the lion back when attacked

subtract a random number from LionHP i suguest between 3 and 7, thats what i have

do a fork option with no excepting case and the condition LionHP below 1

flash this event for 0.4 seconds twice (enter it in 2 times)
play the sound effect monter1 (or another for when the lion dies)
display a message saying how much experience and money you should receive i used 8 for both
do change money increase 8 (or whatever number)
and change experience increase 8 (or whatever number) and show the level up message
set the switch LionLive to off set the switch LionDead to on
then theres the End Case thing

when you play your demo it should have a lion that will chase you who will hurt you if you walk into it or you try to attack it when its facing you and you can hurt it by attacking when its close but not facing you.