Samuel wrote: I don't know how to use LunaDLL....

no problem .
http://engine.wohlnet.ru/forum/viewtopic.php?f=26&t=146 - how to use lunadll
http://www.youtube.com/watch?v=DhnZTL1LroU - tutorial to hp
if you want to make another npc as goomba or . attach mother brain with graphcis of goomba to goomba .
example special for you: big piranha plant with 5 Hp. put this code in lunadll.txt (read tutorial).
SetHits,256,1,-3,0,2,0 (now him hp is 5)
#1 is the section the next codes will activate in
SetHits is the command we want for setting hits
256 is big piranta plat's NPC ID
1 is the section she's in
2 is how much you want to set her hits to. She starts with 0 hits and dies at 2. Setting to 2 will leave her with 1 hits left until 2 ( in my example , if you type -3 its npc's hp + 3)
0 is not used
2 is how many frames the code will run. You only want to set her hits just as you enter the section, so 2 is short enough to set it and forget it
0 is not used