Saint Regalia

Saint Regalia also known as Insignia of the Holy Knight is a very powerful support sacred gear that is shown capable of fusion. Despite being viewed as a very weak or limited sacred gear by many supernatural creatures, with even Ake Raim calling it a "laughable ability" it is revealed that in the right hand it can be a very dangerous weapon.

Summary
Not much is known about the history of this sacred gear other than the fact that it has belonged to numerous kings throughout history thus getting it labeled a "royal" sacred gear.

Appearance
Saint Regalia takes the appearance of a simply black fingerless glove with a blue gem in the middle. During the second stage of this sacred gear however, it grows silver metal that covers the fingertips.

Abilities
The primary ability of Saint Regalia is the ability to interpret, and understand any weapon or ability the wielder scans with the glove. This allows the wielder to understand how the weapon works and how to best fight against their opponent. This however is shown to only be minor ability as the true ability of Saint Regalia is the ability for the wielder to [fuse] themselves with any weapon in their possession. This is shown by the weapon going inside of themselves thus allowing the wielder to use all the abilities of their weapon without having to hold onto the weapon or use it as a conventional weapon, similar to the way Issei uses the Ascalon fused with his boosted gear. Aksel revealed this ability when he infused himself with his own holy sword allowing him to release waves of [support] for Ichiro and Yukina without having to wave the sword around, instead waving his own hand. Aksel is also capable of using this ability with a more battle-oriented sword like Clarent.

Weaknesses
A primary weakness of this sword is that this sword is limited by the number of "special" swords in existence. For example, a ordinary sword that possesses no special ability wouldn't be very useful with this ability due to not having a ability to give the wielder. Another weakness is that the wielder must, not only possess the weapon themselves but be [compatible] with it. For example, since Aksel lacks the ability to wield Durandal, he would be incapable of infusing with the sword as the fusion would put too much of a strain on his body.

Trivia

 * I was originally going to base this sacred gear off of Mastema from Akame Ga Kill but I changed my mind.
 * The image of this sacred gear is based off of the x-glove from Reborn.