Russ mounted priest

If I put a russ mounted priest inside an outpost, does he lose all abilities? if yes, why?

I’m not sure, as I’ve never tried it, but I suspect it would. Else it becomes way too powerful. Putting any unit in an outpost simply gives the outpost an attack ability/ more arrows. If he retains his abilities, this would be a completely new strategy to play. So I doubt it.