The Septuplets

The Seuptuplets are a Post-Moonlord Boss which is essentially just the twins taken to the extreme. The Septuplets are seven separate flying eyes connected by multiple tendrils, each with its own attack pattern and life count. All must be killed in order to fully destroy the boss.

The Twins are summoned using the Mechanical  at night, and must be defeated before dawn, otherwise they will kill every town NPC on the map (including the Clothier, which will then spawn Skeletron Ultimate, which is like skeletron prime but it had 1000 hands which all deal several million damage. While the player is fighting Skeletron Ultimate the Septuplets will blow up everything around the Player's spawn and if the player somehow defeats Skeletron Lucifer, 100,000 Dungeon Guardians spawn. These dungeon guardians are not normal dungeon guardians, because they automatically convert the world into Lifeless Mode, which is like Expert but every enemy has several billion health but all weapons do 1 damage per second. The change always happens, even if you are on Normal or not. If the dungeon guardians are defeated, their death explosions will be so destructive it destroys the entire world except for Hell. Once that happens, 1 billion Wall of Fleshes will spawn, and killing them will result in that number rapidly multiplying, and due to all the enemies your computer will melt.

While The Septuplets are alive, Overworld Day will play.

When it turns morning and the Septuplets are still alive, every single music will be played at the same time and your computer's sound willl be forced onto 100.

Summoning
They are summoned with a Mechanical Nuclear Bomb, which is crafted out of 100 Nukes, which are crafted with 100 Extreme Dynamite, which are crafted with 100 Superdynamite, which are crafted with 100 Dynamite and 100 Celestial Sigils. Approximately, 1 million dynamite are required aswell as 2000 of each lunar fragment.It is crafted at a Death Alter, which is crafted with every crafting station in the game including every variant of Anvils, Furnaces, Forges and Workbenches.

Attacks
Retinazer and Spasmatism are the same, but they just have boosted damage defense and health.

Iricapture shoots no projectiles, but instead rapidly charges at the player with insane damage. When it reaches its second form, it charges until it is dead.

Pupilazer shoots a deathray similar to the Moon Lord Head. It does this rarely in the first form, but it does them every few seconds in its second form.

Ichornea is similar to Spasmatism, but shoots Golden Showers instead of Cursed Flames.

Necroroid in its first form shoots bones at the player similar to a bone glove. In its second form, its hand occasionally reaches out and grabs the player, like Skeletron's hands.

Pinkaract shoots out pink versions of ichor streams, which can be very deadly. When Pinkaract is killed, 50 pinkies spawn.

Trivia
Iricapture's name is a portmanteau of Iris and Capture.

Pupilazer's name is a portmanteau of Pupil and Lazer.

Ichornea's name is a portmanteau of Ichor and Cornea.

Necroroid is a portmanteau of Necro and Choroid.

Pinkaract is a portmanteau of Pinky and Cataract.