The trinity in Christianity isn’t really bullshit, it exist in many pantheons and remain valid in all of them, however, black magick is not a pantheon, the trinity is a general thing among the pantheons, while black magick is just a concept created by people who wanted to feel different from other forms of magick.
Aset isnt a “black magick” deity, she’s a light orientated Goddess of wisdom and magick, while her twin sister Nephthys is a dark orientated Goddess of Death and darkness.
Ishtar is a light orientated goddess of the heavens.
Hecate is a Goddess of death and magick.
You would need to look into their pantheons and see what they are grouped into a trinity with.
Hecate on her own is a triple Goddess, Aset is part of a trinity with Osiris and Horus.
Ishtar/Inanna/Astarte are the same being and is in a trinity with her father Sin and brother Shamesh/Utu.
A person can create their own trinity if the entities involved are okay with working together as a trinity in that person’s path.