The 1.1 update is the biggest update so far in terraria history. This update brings an entire new game mode into the world, Hardmode.
Hardmode is when you defeat a new boss, appropriatly named, The Wall Of Flesh. After defeating this boss, a new biome will randomly spawn
somewhere in your world, named as the "Hallow". The Hallow is the exact opposite of the corruption, being all cute and rainbows and such.
But since this biome was released, the corruption is also upgraded. the corruption can now spread through stone and mud, so be careful about your
base or all of it will be destroyed by the corruption.
The new Corruption is a whole lot stronger than pre-Hardmode. One reason is because of the new enemies, although others may think its
purely because of the augmented spreading rate of it. One of the new Corruption enemies spread on contact of and corruptable block.
As you know, the corruption is just downright annoying because if its constant enemies attacking your NPCs.
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Since enemies are much tougher in hardmode, its time to discard your obolete and old armor, and think bigger.
There are also three new bosses to fight.
The Destroyer