Saix

Saix is number 7 in Organization XIII. He is the Nobody of Isa.

Isa is best friends with Lea who is Axel's real person.

Weapon
Saix uses a large weapon resembling a mace. It's called Claymore.

Kingdom Hearts 358/2 Days
Saix is a playable character in Kingdom Hearts 358/2 Days.

He is also a Boss.

Toward's the end of the game he calls Axel 'Lea' which is his true identity.