if you want to change the defense power of a unique monster, you need to change the parameters server side in the database table _RefObjChar and Media side characterdata_xxx.txt.
if you want to change the attack power of unique, you need to change the parameters of unique skills in the database _RefSkill and media skilldata_encxxx.txt
Use this tool to encript/decript the skilldata_enc.txt
Use this tool to edit skill parameters
Good Luck!