Moon Lord is Terraria's final main-progression boss. The encounter requires destroying the eyes in the hands and head before the core in the chest becomes the final target.
Summoning
Moon Lord appears after the Celestial Pillars are defeated or can be summoned with a Celestial Sigil.
Endgame preparation
- Use endgame-level mobility.
- Bring reliable healing and sustain.
- Choose accessories that support the build's main weakness.
- Use a weapon that can maintain damage while you reposition.
Manage the eye targets
Because several targetable eyes are active during the fight, tunnel vision can be dangerous. Keep track of where pressure is coming from and move before committing to a long damage sequence.
Phantasmal Deathray awareness
The Deathray is one of the fight's most dangerous attacks. Practice recognizing its setup and preserve mobility options so you can respond instead of relying on raw defense.
Final core phase
Once the required eyes are defeated, the chest core becomes the key target. At this point, keep enough healing and movement resources to finish the encounter cleanly rather than rushing because the end is close.
Source: Official Terraria Wiki.