After the corruption gets activated (by either getting "The End" achievement or manually initiating it), 4 corruption seeds will be randomly placed within a 100 block radius of the player. These seeds will nestle them self inside a stone block and corrupt that stone block into mossy cobblestone. From here it will slowly spread to neighboring stone, dirt or grass block (the dirt and grass get converted to coarse dirt and mycelium respectively). The rate at which it spreads decreases as more and more corruption forms, this is to hopefully prevent lag. To get rid of the corruption, simply break the corrupted block, but be aware of it fighting back a bit.

I will be adding more effects later, if you have suggestions of yourself feel free to let me know.

- Will this lag my world?
If you have a decent pc that can run normal Minecraft without any problems this command block contraption will probably not have any significant impact on the performance. I made the randomizer as simple as possible exactly for this reason.

- It does not work, what should I do?
Chances are you did something wrong. Make sure you're using Minecraft 1.10.2 and that you have copied the entire command correctly. If the problem still occurs, send me a PM.

- Can I use this in my own project*?
Under certain conditions, yes. I will allow you to completely use the contraption for your own project, but you must follow some guidelines if you wish to upload it publicly:
1.) You must have made a major change or addition**.
2.) People can not be charged money or be forced to participate in dodgy surveys to view this project. Advertisements on videos and webpages are fine as long as these advertisement can not inflict any harm to the viewer, whether the advertisement is clicked on or not.
3.) You must give appropriate credit to me and link back to this Planet Minecraft post.

* "Project" here stands for any piece of created work. This includes but is not limited to Minecraft builds and showcase videos.
** In the case of showcase videos, any sort of commentary counts as a major addition.