Complex sentence: They proceeded to fight, but Kariya kills her easily and reincarnated her soul to create new Dolls, called Bitto, which the Bount later to used to collect human souls, which can be absorbed by the Bount to gain power.
Split into simpler sentences: They proceeded to fight, but Kariya kills her easily and reincarnated her soul to create new Dolls, called "bitto". The bitto were used to collect human souls, which can be absorbed by the Bount to gain power.