Mysterious Tablet

Type	EnemyInvincible
Environment	Dungeon entrance
AI Type	Lunatic Devotee AI
Damage	0
Max Life	400
Defense	0
KB Resist	100%
Hurt	https://terraria.wiki.gg/wiki/File:NPC_Hit_4.wav
Killed	https://terraria.wiki.gg/wiki/File:NPC_Killed_14.wav

Desktop/Console/Mobile-Only Content: This information applies only to the Desktop, Console, and Mobile versions of Terraria.

The Mysterious Tablet is an invincible NPC which spawns at the entrance of the Dungeon after Golem is defeated. Players cannot interact with it in any way, as it serves only as a graphical prop for the Cultists' ritual and the spawning of the Lunatic Cultist.

The Mysterious Tablet spawns surrounded by four initially passive Cultists, two of them being Lunatic Devotees and the others being Cultist Archers. Once all four Cultists are killed, the Lunatic Cultist spawns, destroying the Tablet and starting its boss fight.

The Mysterious Tablet will respawn (including the Cultists) after 12 minutes (12 in-game hours), if the player runs away or dies during the Lunatic Cultist fight, when all four Celestial Pillars are destroyed, or when the world is closed and restarted. Restarting the world can be the fastest option to reset the Tablet and the Cultists to their original state.

Notes

The Chlorophyte armor's Leaf Crystal may fire at the Tablet, which may lead to the player accidentally making the Cultists aggressive.
The Tablet is not a light source, despite the fact that it appears to be surrounded by a flame-like energy.
The Moon Lord cannot be summoned using the Celestial Sigil if the Mysterious Tablet is visible to any player.^[1]

Trivia

The Mysterious Tablet resembles the Celestial Sigil, a boss-summoning item used to summon the Moon Lord. It appears to have the Moon Lord's face on it.
The Mysterious Tablet, along with the Cultists, can have its spawn slightly changed by moving the blocks directly above and below them.
If the Tablet is spawned in and made vulnerable using third-party software, it can be heard that the hurt sound is the same as the mechanical bosses', and the death sound is an explosion.