When your religion is Pagan, who are the heathans?

Not christians, I'm not ready to bring that in. I need a religion, or a heresy, that's forbidden. The religion I've settled on at the moment is some kind of paganism. I haven't developed it because it's not a plot point, none of my characters are really religious. I've based it off of a modern perception of celtic paganism; gods, plural, blood sacrifices, superstition, druids, that kind of thing. So... my MC's mother was the member of some kind of religious sect that's so hated and/or feared that to practice it is punishable by death. Or worse, my MC's mother practiced it and it's my MC who could end up dead as a result. And when paganism is my religion... who are my pagans?

I think the paganism is more powerful if you have their children as the recipients of the death penalty.

Okay, do you mean your main religion is paganism? And that you are trying to come up with some kind of additional religion the pagans will find objectionable? Assuming that is what you mean and that you don't want Christianity to factor in, I think it could be another pagan sort of religion, perhaps with an opposing "god"...kind of dueling evil religions that each want to assert their god or pantheon of gods is more powerful. The one that your MC's mother practices could be whichever one is currently losing out in the power struggle.

Just a thought.

Well, if one is a very druidic paganism, the other probably ought to be something more Roman. A vague, sort of "romantic" (in the old sense of the word) idealist religion, where as the druidic religion is at once highly mystic and mysterious, but also scientific and formulaic. (Druidic practices have that formulaic side, like a recipe or something.)

The Romanic religion is likely the prevalent force while the druidic religion is persecuted.

Just try not to make the Roman-ish religion much like the actual Romans. Otherwise, it kind of looses the effectiveness.

Does that help, or am I shooting wide of the mark?

I was just going to say that this pagan religion sounds very violent. So maybe a peaceful religion would make them angry?

In my world, one religion worships the sun and moon gods, and it's rapidly spreading rival as atheism/agnostics. Christianity is but a small new religion that isn't widely accepted.

Anyone whose beliefs are contrary to the main religion's beliefs. They could worship animals, the night, they could worship the light, they could be demonic cultists like the Thuggees.

I think everyone has good suggestions. I would define the first pagan religion - the prominent one. What are some of their core beliefs? Then design the heretics to counter those core beliefs. That will give you a logical reason why the two religions are so sworn against each other.

I'm not sure what the basis of your paganism is so I'm not sure if human sacrifice is more violent then they. The best I can do for now is say that chaos and anarchy are always good enemies.