Rejuvenation: if destroyed, its body and equipment blow away as if by a breeze?
Maybe "evaporates into nothingness"?
The weakness is supposed to be silencing the chimes. How do we want to do that? He takes any damage dealt to the chimes? He takes double damage in an area of magical silence?
The original source says "
Keeper: The chimes (all hits are doubled when these are silenced)."
Special Weakness - Chimes (Ex): Each of the seven swords have a different special weakness. The Keeper's is its crystal wind chimes: whenever its chimes are silenced, whether by being within the area of a silence spell or placed in a soundproof container, the Keeper takes double damage from attacks. In addition, whenever a Seven Swords is damaged through its special weakness it must succeed on a Fortitude save (DC 10 plus damage inflicted) or be shaken for 1 round. Should the Keeper be destroyed, the chimes are also destroyed.
I'd be fine with a Ghost Step ability. How do you want to phrase it?
Hmm… how's this for a start:
Ghost Step (Su): The Keeper of the Keys can can shift from the Material Plane to the Ethereal Plane as a free action, and shift back again as a move action (or during a move action). It can also use combine this ability with Ghostly Evasion (see below) to vanish when attacked and move elsewhere, but this costs an Attack of Opportunity and if it fails its Reflex saving throw to evade the attack the Keeper does not shift to the Ethereal Plane. This ability is otherwise identical with ethereal jaunt (caster level 15th).
Ghostly Evasion (Su): If the Keeper is targeted by a melee attack, a ranged attack, or a special attack that allows a Reflex saving throw, it can attempt to avoid it by briefly becoming ethereal, vanishing for an instant and reappearing after the attack passes through the empty space it occupied. The Keeper must make a successful Reflex save against the attack's DC or attack roll, taking no damage on a successful save. It cannot use this ability to avoid ghost touch weapons or attacks that affect the Ethereal Plane. Each use of Ghostly Evasion costs the Keeper an Attack of Opportunity, so it cannot use Martial Parry or make an attack or opportunity when it uses Ghostly Evasion to ethereally avoid an opponent's attack. If its Reflex saving throw fails, it cannot use Ghostly Evasion again that round.
I was originally going to make them one ability, but decided it worked better if I separated out the evasion.