This next idea is the new mode after hardmode: The WORLD'S END Mode.
How it will start
For World's End mode to start, you need to get inside The Dungeon of Corruption. But the door is locked and the bricks can't be mined with any tool, not even a Hamdrax! To get in, you need a Corrupted Key. To make the key, you must have items that the Hardmode bosses will drop (each boss will drop an item that you cannot get in any other way) and a Shadow Key. Then if you right click the locked door with the Key in your inventory, the door will open and you can now go inside. When you enter the Dungeon, the door will be locked shut. The first part of the Dungeon is like the first dungeon, except it is made of Corrupt bricks and it will spawn the Corrupt Dungeon mobs. And, at the end, there is a large square room. Once you get inside, Demonite Skeletron (a new boss) will spawn.
Locating The Dungeon of Corruption
It is found near the ocean opposite of the normal Dungeon. Any Jungles around it will become Corrupt Jungles.
Demonite Skeletron is a corrupted version of Skeletron Prime. He is made out of Demonite and his eyes are purple. He has slightly more damage, speed, and defense than Skeletron Prime. Like Skeletron Prime, his hands have different things on them. His head cannot be destroyed without a weapon with a Holy prefix. His head will drop Corrupt Bones which can be used to Summon him again. (Defeating him again will do nothing new)
Demonite Hand: Just a normal Hand. Similar to Skeletron's hand, just with more speed and damage and will shoot Corrupted Bones which will give the player the Corrupted debuff which is a combination of the Weak, Tipsy, and Confused Debuff. Can knock back the player even with the Cobalt Shield equipped.
Demonite Laser: Will fire lasers at the player.
Demonite Snatcher: Looks like a hand exept when it is near the player, it has a 20% chance to grab the player. Then, Demonite Skeletron will spin is circles and eventually let go of you, sending you flying into the Dungeon wall.
Adamantite Shield: Holds an Adamantite Shield. Has a 50% chance to deflect Bullets and Arrows. Will drop the Adamantite Shield on death.
Demonite Crystal: Will hold the Demonite Crystal and will drop 16-18 Demonite Crystals upon death.
Demonite Crysal and Adamantite ShieldThe Adamantite Shield is an accessory item similar to the Cobalt Shield. It can be used to prevent knockback from the World's End Mode Bosses.
The Demonite Crystal is used for crafting the Hallowed Energy, which requires 15 Demonite Crystals and 15 Pixie dust. It can only be crafted at a Demon Altar. But since there are Demon Altars in the Dungeon, that will not be too much of a problem. But if you break all of the Altars, Demonite Skeletron will either whack you with on of his hands, or fly into you, 1-shot killing you. A new Altar will spawn in the Dungeon after a certain amount of time. The door will also open.
World's End Mode
Killing Demonite Skeletron
The Hallowed Energy is used to make weapons have a new prefix: Holy. Simply combine the Hallowed Energy and a weapon and you get the weapon with the Holy prefix. Weapons with that prefix will act as the weapon's best reforge exept it can destroy Demonite Skeletron's head. (Holy Megashark: Same as Unreal except it can kill Demonite Skeletron.) Once he is dead, Time's End Mode will start and a message at the bottom will appear saying "You are now at war with the Corruption!" Also, the top of the dungeon will EXPLODE!!!
World's End Mode Starts
Once it starts, the Corruption will start to spread through Hallow slowly. Also new Corruption enemies will spawn. Some are...Starved Worm: A worm type enemy. Will follow the exact path your player takes. So imagine if there was an invisible trail that the player will leave behind. When the Starved Worm spawns, it will dig straight to your player. when it is near you, it will begin to follow the invisible trail.
Corrupted Orb: A glowing purple orb that looks like a Shadow Orb. It will spin to warn you it is about to attack. It will shoot lasers in random directions when spinning. Will drop Corrupted Energy which is used for the Corruption Blast spell.
Corrupt Skull: Found in the Corrupted Dungeon. Has the same AI as the Cursed Skull exept it will give you the Corrupted Debuff.
Corrupted Bones: Found in the Corrupted Dungeon. Will give the Corrupted Debuff..
Corrupt Sorcerer: Found in the Corrupted Dungeon. Has the same AI as the Dark Caster exept will shoot Corrupt Bolts which will give the Corrupted Debuff...
Staring Eye: Found in the Corruption. If close to the player, it has a 10% chance to Give you the "Staring Contest" Debuff. With this debuff, all nearby Blinkless Eyes will stare at you. You cannot move with this debuff active. Eventually, the screen will go foggy and the Eyes will fly towards you and attack. To stop the Debuff, simply hit the Eyes staring at you.
How to stop the Corruption
To stop it, you need to talk to the Dryad. She will tell you to buy Anti-Corruption Blocks. These Blocks will slow down the spreading of Corruption. Also the Guide will tell you to look out for Hallow Ghosts, which is a mob that will spawn in Hallow taken over by Corruption. They look like yellow Wraiths. They will drop Hallow Crystal which is used to make a Boss summoning item. When the boss is defeated, all of the Corruption will be replaced by Hallow.
New Bosses and Weapons
Corrupt Blast: A mana weapon. It will take 200 Mana. When used, it will create an explosion that will harm enemies and PvP players, but not you or any Blocks. It has a 20 second cooldown.
Dark Murumasa: Found in Corrupt Dungeon Chests. it is a World's End Mode version of the Muramasa. It is faster and stronger than the normal Muramasa and inflicts the Corrupt Debuff
Red Moon: World's End Mode version of Blue Moon. Exactly like the Dao of Pow but with the Corrupt Debuff, not the Confused Debuff.
Hallowed energy: Used for defeating all of the Time's End Mode Bosses.
All Seeing Eye: World's End Mode version of Eye of Cthulhu. He is 5 times larger than EoC. He will shoot out Wanderng Eyes and an Explosive Eye which will follow the Starving Worm's AI and will explode on impact. At half health, he will spin and start shooting Corrupted Orbs and Staring Eyes.
DeathWorm: Corrupted version of the Destroyer. It will dig faster and it is stronger. Made out of Demonite. can spawn a Staring Probe which has the same AI as a Staring Eye exept it fires lasers, like a normal Probe.
Wall of Corruption: Can be summoned by smashing the Corrupted Orb in the Underworld found after defeating Demonie Skeletron. But you need an Ultra Hammer to do that. It is made from a Pwnhammer, 70 Hallow Shards, Giant Lens, Staring Probe, and a Demonite Crystal. The Wall of Corruption has 180,000 health. It will move extremely slowly, so you might me able to defeat it before it crushes you. It's Eyes are like the twins. The top shoots fire, and the bottom shoots lasers. The mouth spits out Metal Worms which are small versions of the Destroyer. When killed, the World's End mode will end and the most of the Corruption will dissapear.