In Damage, Fenrir is the strongest, but in overall, Ultima Weapon is unbeatable.
the strongest blade is the cold rune edge lol jking
Evil Beafaol
Falcon blade
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You have to use the blade key that removes from your black smart key. There is a tumbler right next to the release handle, you can use the blade key and open the trunk
you use a key ring
The Chaos Blade, which you receive in one of the last battles in Muround.
Depending on your blade - you probably sheared the shear rivets, bolts or key.
Theres something that resembles a Keyblade on Gaia its called the G Blade or Keytarblade. Hope that helps.
You get it after the partner battle wioth Axel.
The Brightcrest
It is the unbound.