Well, she can't attack him at an FW haven, right? The attack would be canceled.She can't move to hero haven anyway, if he squats at a fw haven he's likely to be there doing multiple stuffs, HoF is easily dealt with by Eye of Sauron V, maybe he sits alone so she can attack him every turn...so nerf?
I don't think Eye of Sauron is enough of a counter, because Eye can itself be countered. I don't like the idea that an Adunaphel Unleashed strat is much weaker against squatter decks, of all things.
If you really think the circumstance warrants it, we could say:
Playable on Adûnaphel (as your Ringwraith). Discard this card to untap Adûnaphel.
Alternatively, you may tap a lone Adûnaphel to place this card with opponent’s tapped non-Wizard, non-minion character at the same site. Dark-enchantment: Character may not untap as normal during the untap phase (or by Hall of Fire) or move. If placed on opponent's character, discard this card if Adûnaphel is wounded or moves.
Cannot be duplicated on Adûnaphel or in an opponent’s company.
Is that cool?