He's a tough one, but not impossible:
1 Ash's dispel to remove his defense boost, and regen will really help
2 character levels should probable 13-15 (15 is max lvl in this version)
3 The MC's monster forms lvl independently of the character.
4 the chimera system in this version allows you to take traits from other forms (for example hp slime form poison spit or hp boost added to MC's wolf from)
5 Lyric is your healer, but Ash can also use blood drain to help recover hp.
6 stock up on elixirs for quicker recovery
7 bleed from MC's ripper skill seems to do more than poison, corrosion, or curse for damage over time.
8 give the shelter ring to Lyric he's to help him tank some of the Fairy Prince's attacks.
other than those all I can say is the fairy prince has at least 3000 hp minimum, so be prepared for a drawn out battle.