Explains why the Lunatic Cultist sounds like he is saying, "How did you know?" when he spawns in to take the power within the tablet. Before fighting you, he wonders how you knew to come there and stop them from doing what they were doing.
Terraria Community Forums
Techhunter_Talon
Techhunter_Talon
Thinking on it, maybe the Lunatic Cultist and the Moon Lord are one and the same.