Celestial Pillars

Each pillar has a protective shield that must be broken by defeating 100 of its unique enemies; after all four pillars are destroyed, the Moon Lord spawns.^[1] Each pillar has 20,000 health, 20 defense, deals no contact damage, and is immune to all debuffs except whip debuffs.^[9]

Short entry: this is all the Terraria Wiki page states about it so far. Read the wiki page.

Quick Facts

Type: Boss
Environment: Lunar Events
AI Type: Celestial Pillar AI
Damage: 0
Max Life: 20000
Defense: 20
KB Resist: 100%
Immune to: All debuffs except whip debuffs

Facts from the infobox of Celestial Pillars on the Terraria Wiki (wiki.gg, CC BY-NC-SA 4.0).

Solar Pillar

The Solar Pillar is melee-themed, has the largest variety of enemies, and its minions include the Crawltipede, which only targets airborne players.^[2][3]

Vortex Pillar

The Vortex Pillar is associated with ranged combat, its enemies can apply the Distorted debuff, and it stands alone as the pillar where neither enemies nor projectiles can pass through blocks.^[4][5]

Nebula Pillar

The Nebula Pillar is magic-themed, has the fewest unique enemies, and its minions can teleport and attack through blocks.^[6]

Stardust Pillar

The Stardust Pillar is summon-themed, can spawn extra enemies from constellations, and its Star Cell enemy splits into smaller versions when killed.^[7]

Pillar spawning mechanics

After the Lunatic Cultist is defeated, the pillars appear at four positions evenly spaced across the map, with a random horizontal offset of up to 100 tiles.^[8]

References

"Celestial Pillars" (opening section) - Terraria Wiki on wiki.gg, revision 1031403 terraria.wiki.gg
"Celestial Pillars", section "Solar Pillar" - Terraria Wiki on wiki.gg, revision 1031403 terraria.wiki.gg
"Celestial Pillars", section "Solar Pillar" - Terraria Wiki on wiki.gg, revision 1031403 terraria.wiki.gg
"Celestial Pillars", section "Vortex Pillar" - Terraria Wiki on wiki.gg, revision 1031403 terraria.wiki.gg
"Celestial Pillars", section "Vortex Pillar" - Terraria Wiki on wiki.gg, revision 1031403 terraria.wiki.gg
"Celestial Pillars", section "Nebula Pillar" - Terraria Wiki on wiki.gg, revision 1031403 terraria.wiki.gg
"Celestial Pillars", section "Stardust Pillar" - Terraria Wiki on wiki.gg, revision 1031403 terraria.wiki.gg
"Celestial Pillars", section "Pillar spawning mechanics" - Terraria Wiki on wiki.gg, revision 1031403 terraria.wiki.gg
"Celestial Pillars" (infobox) - Terraria Wiki on wiki.gg, revision 1031403 terraria.wiki.gg

Text adapted from the Terraria Wiki on wiki.gg (CC BY-NC-SA 4.0), used by Freedom Games LLC, the operator of wiki.gg and Codexery. Page: Celestial Pillars (contributors). Codexery summarised the page: each numbered sentence above was checked against the wiki section it cites before publication, and this entry is shared under the same licence.