Real

The Old Testament talks about the three of them. Why would herasy happen?

Because describing the Trinity without commiting heresy is very difficult.

Describing the Trinity as something like water: "ice, liquid, and vapor"(which I've heard some do) would be heretical and wrong. If, however, we discuss them as laid out in the Bible, with reverence fot the mystery contained within their unique selves we should be okay wouldn't you think?

That was my point. Most people unintentionally describe the Trinity in a heretical way

😌👍

Real, Thomas Aquinas probably did it the best tho