The All in one, the One in all. The opener of the way. The Beyond One. The Key and the Gate. The Lurker at the Threshold. All of these are the names of one of the most powerful entities in the Cthulu Mythos universe, the Outer God Yog-Sothoth. Out of all Lovecraft’s creations, he’s the third in the trinity of the most powerful cosmic horrors (who’s more powerful between him and Nyarlathotep is debatable.) Yog-Sothoth is of the most ancient eldritch horrors and commands tremendous power beyond human comprehension. The entity is the master of space-time and exists beyond our physical plane, seeing all realities of the multiverse at the same time.
The Outer God has a long list of powers and abilities that to comprehend, any mere human would be instantly driven insane. The eldritch horror has powers like omniscience, omnipresence, telepathy, invulnerability, and the ability to warp reality itself. He’s a descendant of Azathoth and the offspring of the Nameless Mist Outer God, who’s Nyarlathotep’s sibling, and Yog-Sothoth is the grandfather of Cthulu himself.
“Yog-Sothoth knows the gate. Yog-Sothoth is the gate. Yog-Sothoth is the key and guardian of the gate. Past, present, and future, all are one in Yog-Sothoth. He knows where the Old Ones broke through of old, and where they shall break through again. He knows where they have trod Earth’s fields, and where they still tread them, and why no one can behold them as they tread.”
This Outer God has a bunch of different forms and appearances he can take on, just like Nyarlathotep. Though, his ability to do so is MUCH more limited. He doesn’t have nearly as many forms as the Crawling Chaos.
Yog-Sothoth is a massive cosmic entity dwarfing almost all others other than Azathoth himself. But the entity’s true form is far beyond human comprehension. Many writers other than Lovecraft have written about him, with descriptions of the eldritch horror varying often. Though, there are usually similarities in the way he’s depicted in the Mythos Universe. Yog-Sothoth appears as a mass of glowing orbs of countless sizes. Sometimes with flaying tendrils sprouting everywhere with a bubbling mass of eyes which are constantly changing form. The tendrils often have many sharp-toothed gaping mouths morphing into existence only to meld back into the swirling appendages. Yog-Sothoth’s form is in constant flux and change, just like the countless universes he sees all at once. However, a couple of the entities forms appear humanoid, though his features are hidden behind a shimmering veil.
This Outer God isn’t outright malevolent to humans like many cosmic horrors in the Mythos. If anything Yog-Sothoth is neutral, but trying to define any of Lovecraft’s creations with human morals is laughable. Though the deity has no problem interacting with humans and even seems to enjoy it (in a twisted sort of way.) He’s one with all space-time, but unlike his uncle, Nyarlathotep is blocked from entering the material plane. So Yog-Sothoth can’t willingly set foot on Earth. An aspect of the Outer God can, however, be summoned into our reality. And since he’s in all time, past, present, and future in all planes of existence in the multiverse all at once, Yog-Sothoth has countless cultists and worshippers throughout all eras of history.
There are no secrets to Yog-Sothoth. He sees all, knows all, hears all, and sees inside the minds of all. This Outer God may not be the most powerful entity in the Cthulu Mythos, but he’s without a doubt the most knowledgeable. So many seeking forbidden knowledge and secrets of the universe seek out Yog-Sothoth. He possesses a level of intelligence far greater than human comprehension. A human trying to talk to the Outer God is analogous to an ant trying to talk to a human. He’s just an intelligence beyond what our small human brains can even remotely grasp. Though whatever knowledge the entity may give, it comes at a steep cost. Human life must be sacrificed, and unspeakable acts committed to gain Yog-Sothoth’s attention (though this isn’t always the case.) People summon Yog-Sothoth for many reasons. Sometimes even to simply gain power or a little influence over space and time. However, trying to use the god for personal gain can be a risky business. Anyone who tries to screw with time or alter reality will end up face to face with Yog-Sothoth, who will punish the transgressor in a fate worse than death, or worse than…. anything really. Pissing off an entity who can trap you in infinite time loops of torment is foolish, to say the least. But those who practice the occult, sorcery, or anything of that nature in the Mythos Universe often seek out contact with the Lurker At The Threshold.
In the story “Beyond The Gates Of The Silver Key” the protagonist gets to straight-up talk to Yog-Sothoth while journeying through the multiverse. Though the entity was first mentioned by Lovecraft in the story “The Case Of Charles Dexter Ward” but became a common component of the Mythos from that point onward. However, the most famous story with Yog-Sothoth is probably the Dunwich Horror, in which the entity actually impregnates a human woman, and fathers to mortal twin sons.