The manual says this: "as hero cards cannot move to a player’s hand or deck." (pg 20 under Hit Points and Damage)
Maybe this means you cannot trigger any effect that would move the card with Sword-Thain back into your hand or deck. Or you could trigger it, but the part of the effect that would move the hero would just fail.
If this is correct, that would mean...
-Can't use Landroval's ability (the cost is to return him to your hand)
-Put Spirit Bofur into play via his Quest Action, then somehow manage to get Sword-Thain onto him (Vilya) and he will stay in play regardless of quest outcome
-Put an expensive ally into play via Sneak Attack or a dwarf via To Me! O My Kinsfolk!, then give them Sword-Thain and they will remain in play. Or Gwaihir's Response could accomplish the same thing for Landroval. Very nice for ally Beorn because then....
-Trigger ally Beorn's action without having to shuffle him into your deck
Edited by GrandSpleen