Heh. The odd one out.I honestly don't remember where I got the original idea for her.

She was included in the first Vas Diaboli iteration and was in a quite important role in it. She was the only one who needed absolutely no redesigns or adjusting.

Only thing I did add, was giving her the 'infected' look which differs from her natural feline colors. So she can disguise herself like the others, despite not being really a vessel; she is still infected non the less.

Her connection to Tamer stems from the fact Tamer used the cat as a temporary vessel, but was unable to adjust. Traces was left behind when he made the jump to Charity's original owner (previous Tamer).
Ever since she has been following Tamer quite loyally - even when the host/vessel changes.