The very first Keyblade many know and held that 1 fateful day...
The passive particle effect has 3 stages to it (reached at combo counter 10, 25, 50) where it will increase its emission.
Custom particle on Slice that attempts to give the feeling of Kingdom Hearts 1 particles.
If you rather not have the hit particle when slicing, you can disable it by toggling off events in saber factory (this will default the passive particle to stage 2 where it will stay).