Everyone thinks Grotarons are animists, but I'm convinced they have a strong mystical tradition. They have a third eye, after all, even though it's in the back of their hand (like the other two), and are prone to hallucinating. They also lead a cloistered existence, but that's largely because most Gloranthaphiles took one look at them and decided they'd be buggered if they were going to let them out into mainstream Glorantha.
A bit like ducks, who are also mystics.
The invisible sabre-toothed mountain-hopping mammoths they hunt/worship are definitely mystics. If they even exist. I've always wanted to play one. This is primarily because I tend to misread 'Misty Mountain Hop' as 'Mystic Mountain Hop', and use it as their theme tune.
Stew.