Current Events > Terraria hard mode question

(+) Yeah! (+)

It's been a while since I played but the last thing I did was make it to hard mode. I remember reading something about something growing (as in grass or a type of rock or something) out of control if left unchecked but I don't remember the details.

So, what is it and what should I do to keep it from becoming a problem? I don't want to play again until I know what to do about this.
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The Hallow and Corruption/Crimson spreads out of control after you beat the wall of flesh, only way to prevent it is to dig on both sides of the world a huge (10-15 wide) hole so it stops the spread... kinda

The other solution is using an item called the clentaminator, works like a flamethrower but removes corruption/crimson and hallow.

Honestly it's not a huge deal, you could just dig a hole on both sides of your house/spawn point just to be sure your underground will be clean, but do consider that both Hallow and Corruption/Crimson spread in a V pattern from their respective biomes all the way to the middle of the world so it will spread eventually regardless of how many prevention measures you take, but then again as i said, you can just take your time with the clentaminator and clean everything.
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When you begin hardmode, two giant stripes of the corruption/crimson and the hallow make a V shape across your world. You can dig giant ditches around them and completely section them off, or use the clentaminator to purify them, and I think killing Plantera (the underground jungle boss) greatly reduces biome spread as well.

I personally dig ditches, though keep in mind, when you use the pwnhammer to destroy demon altars to place hardmode ore in your world, each altar you destroy places a block of corruption/crimson somewhere in your world and it'll start spreading.
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