The Mindless Almighty

So, isn't this terrifying? I'm terrified too... Giygas cannot think rationally any more, and he isn't even aware of what he is doing now. His own mind was destroyed by his incredible power...What an all-mighty idiot! —Porky Minch describing Giygas, EarthBound

A (usually) mortal being falls to the temptations of attaining significant and often god-like power and eventually succeeds; but where temptation proved too great for them, the power proves ten times more so, and they begin to literally lose their mind. Sapience, sentience, individual will, sense of self—at least one of more of these will end up buried or destroyed, possibly completely, from sheer force of intake. Alternately, someone who is already a deity (or at least strong enough to be one) undergoes a further enhancement that pushes them beyond their bounds, eroding their mind and/or soul - often until they're an empty shell of their former self.

In summary, With Great Power Comes Great Insanity and the potential to create an Unknowing Almighty. The name is derived from the phrase "all-knowing, all-mighty", often used in reference to the Judeo-Christian God.

The Unknowing Almighty is a being with god-tier power or better, but at the typically direct cost of severely diminished or nonexistent capacity for cognition - effectively, an omnipotent vessel driven by nothing but the most instinctual impulses. Aggression, rage, simple curiosities, and hunger are some of the most common ones. This state often draws comparisons to that of a wild animal or a child... at least by human standards, anyway.

Many animals display their own form of understanding and self-awareness in ways we humans have yet to fully understand - but even the most "intelligent" animals are still incredibly dangerous if they go feral. The idea of such a ravaged mind being likened to that of a child is technically more accurate: in psychoanalytic theory, the mind of a newborn child is regarded as the purest form of id. If the deity is a literal child, that's Goo-Goo Godlike.

Becoming an Unknowing Almighty may transform the victim into an Eldritch Abomination if they weren't one already. Cosmic Horror Stories employ this trope frequently, as monsters like some of the Elder Gods can be far more frightening when they're not acting out of malice - any morality or intelligence they possess (if any at all) might be completely alien to us, and the concept of our own existence might not even occur to them.

Compare:

• Mad God, which overlaps significantly due to the base concept of "deity whose mind is shattered".
• Tortured Abomination, where a sufficiently strong Eldritch Abomination is subjected to enough torture that they are rendered 'feral' enough to lash out (or worse).
• Severe cases of Superpower Meltdown or being Touched by Vorlons.

Contrast:

• King of All Cosmos, where the deity is more highly eccentric or outright weird than anything else, though it's still possible that their mind is fried besides that.
• Goo-Goo Godlike, when a being with god-like power is still in the actual stages of infancy, which still has potential to overlap with this.
• A God I Am Not, for characters who are fully aware of their godlike powerm but still have the humility (and thus 'sanity') to refuse to think of themselves as such.

Laconic: The result of cramming phenomenal divine power in an itty-bitty mental space.

Examples of The Mindless Almighty include:

Comic Books

• In the Preacher comics Genesis is revealed to be an example of this once Jesse learns more about the being and why it came to choose him as a vessel.

Literature

• A classic example is Azathoth from the Cthulhu Mythos, literally referred to as the "Blind Idiot God". Where Nyarlathotep was actively malicious towards humanity to a degree, and Cthulhu even had aspirations to bring back the Old Gods, Azathoth is far beyond either of them in power, but comparatively utterly lacking in motive of any kind. H. P. Lovecraft conceived it as "The Nuclear Chaos" that mindlessly drove the forces of physics and may have created our universe - and as such, it embodies it quite literally.
  • Where Lovecraft conceived Azathoth as the eternal chaos that is, was, and will be, later writers made it so that this wasn't always the case, and instead became that way upon losing its mind; August Derleth in particular portrays this as divine punishment from the Elder Gods.
  • Azathoth also reproduces by fission, as does its offspring - it's not uncommon at all to liken ol' Azzy to the universe's most powerful amoeba.

Video Games

• The final boss of EarthBound, Giygas, is described as such by his Dragon Pokey Minch, who released him from the Devil's Machine (which was likely keeping his sanity tethered to him in the first place). His attacks are preceded by completely random statements in this form, and the attacks themselves are the Trope Namer for You Cannot Grasp the True Form. (Though depending on your party's loadout, you might recognize them as actual PSI attacks - particularly PSI Flash and PSI Thunder, which can be blocked by certain items.)