if your haveing trouble defeating the last boss, get the kings armor, the best melee weapon, and the best bow, and plenty of throwable shurikens, and stay up in the corner with the bow and shoot him, and switch to the axe in case he respawns behind you, repeat this in either corner of the map and you should win, it worked for me...
the life upgrade kind of increases your defense, strength adds on to the chance of hitting critical and overall damage you can do, and energy makes it so you do special and burn less energy...
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