So my question is: why does "God" refer to himself in plural? (Let us create...)
I did some research, and the Trinity isn't even mentioned in the Bible (at least not as "Trinity", there are hints of it). Why would a "God" that claims to be only God refer to what looks like others like him (as if he was one of many; "our likeness")?
*I'm an atheist (just in case)
It has nothing to do with the Trinity, it has to do with the masculine/feminine nature(s) of Elohim.
What many people do not understand about both 'creation' and 'creator god' is it involves a relationship between two polarities: masculine (male) and feminine (female). It is thus written that Elohim has an image (+) and a likeness (-) that is male and female.
'El' is the general "towardness" or active principle. Example: "towardness" in sperm.
'im' is the general "medium" or passive principle. Example: moisture in womb.
So the word/name Elohim is the conjunction of seed and womb: where one and one come together to produce another one. This is why Elohim, when speaking, address themselves as "us" however when referenced from the outside (such as in Genesis 1:1 the preceding 'bara') it is treated as singular.
When man and woman are united under a shared will: such that will to bestow (phallus) and will to receive (ovum) are wholly balanced, they culminate into one 'thing' which, by virtue of there being both polarities that sustain each other, leads to
creation ad infinitum: the eternal life.
That is the nature of the creator god Elohim: both male and female as one. This is why the primordial Adam was made both male and female in the image and likeness of Elohim. They then undergo the separation of sexes such that these two polarities are embodied in unique bodies.
Now of course they don't teach this in the Abrahamic religions because such religions are progressive perversions of such notions that bind adherents into adopting Patriarchal idols such as Jesus and Muhammad. The former had their wife disregarded by the Church, whereas the latter had many many wives and sex slaves. This is why the world is f*cked - people need to stop worshiping these idols and understand how creation actually works.