One of the five elemental Patternblades, Merehallow is one of the blades that was guarded by Daffyl, the guardian serpent for many centuries, within his tower hidden in Shadow.
Merehallow is a silvery-white blade with a black tracery upon it, depicting a portion of the Pattern. Its hilt and crossguard is made of a grey metal, engraved with stylized depictions of the winds and clouds. The grip is solid crystal, with a golden pommel representing the shining sun. The blade itself has power over Shadow-travel, allowing even shadow-dwellers to travel among the Shadows as if they were an initiate of the Pattern, as well as sensing the movements of others through Shadow. What other shadow-manipulation abilities it might possess have yet to be discovered. Merehallow also has the usual suite of Patternblade abilities -- high damage value, spellbreaking, setting Chaos blood aflame, etc.
Merehallow awaited the "Ever-Burning Brand" to draw it forth to bear it to battle; there is still some debate as to wether Morgan or Kanna would have qualified at one point. (Morgan is the daughter/son of Hiko, the Child of Fire and the Green Knight, the Protector of Arden; while Kanna is the daughter of Corrine, the first Warden of Arden (and potential Child of Wood at one point) and the Red Knight, the Protector of Ember. Both of whom represent a union of Wood and Fire, constantly burning and rejuvenating). However, the point became moot as Morgan was able to draw the blade from its confinement on the eventually disasterous recovery mission from Daffyl's Tower.
Having recovered Merehallow, Morgan attempted to learn more about the blade and to try and deliver it to Juri in Cathuria, but when the Phoenix's Egg failed to hatch, she instead decided to try and retrieve the other missing patternblades, such as Withywindle. This led to a deadly ambush on Endor by the faction of Serpent's Horn which was now under Daffyl's Control as well as Lord Alars (who was wielding Justice at the time). Lord Alars lost his life, Morgan lost several limbs, and the Sword of Air was claimed by House Alars by Chaosian right-of-battlefield claim.
House Alars held onto Merehallow for several weeks, locked away until the Serpent's Horn faction once again struck, this time stealing the Sword of Air. It was then weilded by the red-headed gold-eyed warrior Kenshin in their various assaults on other Houses of Chaos and Amberites in their attempts to recover Justice and to punish all those related to the group who had stolen the blades in the first place.
Finally, in a group extraction/recovery/assault mission involving the armies of Amber, House Helgram, and House Nurgal, the Sword of Air was finally recovered from Kenshin's hands upon his death. It then passed into the safekeeping of Kanna, who successfully delivered Merehallow to her Aunt Juri, despite such interruptions as giant Black Unicorn Amber War Trains and Yog-Y'bootymac/House Tremere collaboration.
Juri now possesses Merehallow and is expected to hold onto it, as everyone will cry if she does not.
Juri not only held onto Merehallow but used it to slay Hel on the Day of the Dead, after being fired out of a torpedo tube at her. It remains in her possession.