Bond of Flame

The Bond of Flame is a Keyblade given to Sora by Axel after he sacrifices himself to save Sora from the Nobodies in Betwixt and Between in Kingdom Hearts II. As the name suggests it may represent Roxas and Axel's friendship. It enhances fire-elemental attacks. This keyblade also appears in Kingdom Hearts Re:Chain of Memories as a card in the Halloween Town Key to Rewards Room.

Appearance
This keychain, teeth and blade resembles Axel's chakrams. When you attack with it, it shows Axel's weapon. Connecting the two chakrams appears to be an eight, possibly referencing Axel's position as Number 8 in Organization XIII