Consider maximizing your defence before triggering the boss fight. Make sure ypu have either End-Game Weapons, or Celestial Weapons. I recommend the Solar Eruption, Star Wrath, Meowmere and/or the S.D.M.G. Take Luminite bullets with you! After triggering the fight, warp strange back home where tnere is a nurse! Don't worry about tne boss despawning. He will warp to your location after you warp. ↓