a little help please

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MemberOvomorphAugust 07, 20121045 Views3 RepliesI just read At the Mountains of Madness and I have a question.
What chases them at the end? is it a shoggoth and what exactly is a shoggoth?
Is Chtulthu an "old one"?
What should I read next to further my understanding of these things or was it all in ATMOM story?
Thanks.
ALL generalizations are WRONG!