Symbolism is the use of symbolism as a way to convey meaning. A lot of ideas are left unexplained in current entertainment, especially in the media that in their approach to storytelling a lot of questions are left unanswered. Fans of the book or series get to answer questions like: Who is Jon Snow ? What is the relation between his parents, Ned and Lyanna? What was the past life of Theon Greyjoy? What was the destiny of Arya Stark and her father/brother? The whole sub-plot about Bran wanting to escape Winterfell through a horn of winter works because it is a metaphorical device for the audience.
Just like in the symbolism of the shape of two hands, this horn symbolism works in the same way that the “eternal formula” also works as a real 3-dimensional blueprint for any figure.
So, we’ve seen the triangular shape in old art and it looks a lot like the pattern from the Apocrypha, but just as it has not been translated into a symbol, we cannot say that it is a symbol of the Holy Trinity. There are some people who think so, and in truth this really doesn’t matter because no one can make the above secret symbols rhyme any more than an ordinary puzzle can do. I would just like to point out to all Christians that although this piece does look a lot like a pentagram verse from the Bible that “Danger no man” was a theme that Christians have been hearing since the time of the apostles. So we must interpret this symbol in a “literal” sense to know the point, but we must also take into account its “platonic” nature. What I mean by this is that if you consider the Hebrew code word in which this symbol is made, it looks exactly like the letters of the word “Jesus”