Lunar Events

The Lunar Events are a series of four Hardmode, post-Plantera events initiated by defeating the Lunatic Cultist boss. Once the boss is defeated, several surface biomes show a large moon in their backgrounds, and spawn several unique enemies. The moon biomes will spawn in four distinctly spaced sections of the world. Defeating the pillar will revert the area back to normal. In order to defeat any of the four pillars, one must first kill many monsters corresponding to the selected pillar in order to remove the barrier that is protecting it. To find where these pillars are, open your map. There will be icons of each pillar which will show where it is.

Each of the four variants has a different theme, along with a corresponding Celestial Tower variant that acts as the centerpiece of the event.

Upon defeating all four pillars, the message "Impending doom approaches..." appears in chat. The screen begins to shake, and approximately one minute later the Moon Lord will spawn on top of the player.

Tips

 * Destroy the Nebula Pillar first, as it grants access to the Nebula Blaze, an extremely fast and powerful homing magic weapon that will help take down the other three pillars. The Nebula Pillar can be easily taken down with a Razorpine and healing variant of the Spectre Armor.Another option is the defeat the Vortex Pillar and get the very powerful Vortex Beater, which with Shroomite Armor equipped, you can easily take down the other three pillars.
 * When fighting the Solar Pillar, take into account that the Crawltipede does not target players on the ground. Knowing this, you can easily defeat the pillar while staying on the ground