SCP Foundation

This is definitely dripping with lore, and does a pretty effective job of worldbuilding through the associations of this creature's past.

As it is wildly different from the standard formats I'm familiar with, and I have very limited experience with SH articles, I will point out only the parts that stand out to me as at-odds with the rest of the article, or grammatically out of whack.

still growing army.

still-growing should be hyphenated.

for his brutal relentless assaults

Comma after brutal

mindlessness lead to his fall

Past tense of 'lead' is 'led'.

stated to be of massive size, and no exact measurements

I feel like "but" would work better than "and" here.

Goran is mindless in his pursuit of destruction, though he maintains a moderate level of sapience.

Minor nurgle, but I feel like 'near-mindless' would work better, since it goes on to explicitly state that he isn't wholly mindless.

One or two blows from Goran is enough to lose to him for most.

In order to better fit the tone, I recommend "One or two blows from Goran is enough to fell most any foe." or something similar.

It is not known how long Goran has existed or his true origin.

comma after existed.

(See Library source on the Great Abyss)

This stands out as the only parenthesized bit, it might work better as a footnote, perhaps expanded with a bit of in-character commentary.

Reason why he would be within the Great Abyss

I think the sentence should begin with "The"

He became very favored by the Scarlet King,

"very" could be removed to improve the flow here.

and was being considered to posses authority of all forces.

similarly, 'being' could be removed.

especially of those with different tactics than Goran.

Recommend: "especially those who favored different tactics than Goran."

At an unknown time, Lord Goran became imprisoned when attempting to conquer a universe conquered by an Archon of Yaldabaoth.

A form of "to conquer" is used twice back to back; recommend changing one of these to a different verb, perhaps a universe already subjugated by the Archon.

banishing him to an unknown plain of existence

I believe this should be 'plane'

The Archon lied and a conspiracy is under way. This claim is entirely baseless, and deemed incredible unlikely.

"incredible" should be "incredibly".

"I like to propose something.

"I" should be "I'd"

All in all, a very fun read, brimming with some pretty badass imagery.