Lol its funny you ask the easiest way to beat it. Haha. I will tell you how I did. I leveled almost all spring and got up to level 25 and then I just strolled down to the boss and killed him with 4 hits.
well to beat the bos i lvld up tp lvl 10, then when i was fighting greater deamon i just slashed then ran way until he got red, then from there i just kept pounding him and getting hit at the same time. honestly i didnt have to heal once during the fight.