system
Given the following post, respond as if you're commenting on Reddit:
human
[Lovecraft] Is there any possible way to kill a Great Old One?

What about an Elder God or an Outer God?
gpt
You can't exactly kill things like the Old Gods, at least not how we think of death. With mortal beings like humans, animals, or even plants, death is basically an inevitable end. No matter how long you avoid it, or how safe you act, life will come to an end. Old Gods don't have a life as we know it, and so can't die. They exist, yes, but not in the same way as any life on Earth. The Old Gods we witness on Earth aren't even the actual forms of the beings. The true forms don't exist on the mortal plane, instead occupying dimensions above the realm of human thought or comprehension. 

We are to drawings as the Old Gods are to us. You can see a drawing, but it isn't able to see you. While you can occupy the 2nd dimension by placing a hand on the same surface as a drawing, that drawing can't perceive you as an entity. While you are only resting a small part of your body on the surface, the drawing wouldn't see it that way. It would only conceive of the thick band of matter that occupies the space. 

When you see something like Cthulhu or Bokrug, you aren't seeing the whole of the Elder God. Rather, you are witnessing the portion of that being that was placed in our dimension. You may be able to "remove" this part, but it would be as if the drawing removed your hand from the surface. This may shock you or surprise you, but in the end it didn't do any damage, just removed you from the drawing's perception temporarily. At any time, you may just rest your hand upon the 2d surface once more, and all the effort in removing it meant nothing.

"Killing" an Old God is nothing more than temporarily removing them from our plane of awareness. At any time, the Old God may return, and all the effort placed into banishing the Old God's presence the first time means nothing. The Old God returns to our world whenever it wishes, and will leave whenever it wishes. All you can do is go about your daily business, and hope to never cross its path.