Flow Invader

The Flow Invader is an enemy that spawns near and is summoned by the Stardust Pillar during the Lunar Events. When it spawns, three smaller minions will appear one at a time and begin orbiting it. The Flow Invader uses these as attacks, sending them as 1-2 high speed projectiles towards the player. When it dies, it will shoot 3 projectiles as a final attack. The orbiting minions will reappear over time. It will launch all its remaining minions at the player upon death. If the Flow Invader is killed shortly after it spawns, fewer minions will be launched at the player.

Trivia

 * It seems to resemble a miniature, bluer version of the Moon Lord's head.