[Alneyan]

An Astral 1 Capricon wasn't Mind Dueled on the land, so it looks like you do need Astral 1 or better to be targetted by a Mind Duel. (My astral mage overrode my script, and cast Luck, Paralyse/Mind Burn/Paralyse/Mind Burn)

Still about the Capricorns, they have a limited Stealth ability on the land. If they move from a water province to a land province, they can still hide (you will have to click on the province to put back the hide order though), and so will not be attacked even with their Stealth gone. They cannot move either, so they will have to stay lurking in the province, or to try taking it.