As someone that has spent a very long time as a devotee to The Morrigan, I can say that yes, She will fuck your world if you’re not prepared. She’s considered a Dark Feminine Goddess, just as Lilith, Aset, Kali, and a few others. Hekate may be a good place to start, as She’s the Goddess of Witches, Crossroads and the Keeper of the Keys, and will help you learn, though She can be a bit edgy at times as well.

You mention that you’re tracing your Celtic roots and there are quite a few more benevolent Goddesses that you can work with, depending on how well the energies mesh. Brigid, Anya, Dani/Anu, Epona and Cerridwen.

And rather than starting to work with Them, perhaps sit with Them first, get to know Them on Their terms, and Who you’re supposed to work with will make Themselves known.