Like any modern day Hell Kat, Tanako is able to alter the Empathy of others in such ways that she could turn friends into violent enemies, and corrupt their ways of thinking to make them fall to the darker sides of their personalities. Anyone who meets her gaze will find themselves depleted of most of their energy, as meeting the gaze of a Hell Kat causes soul damage to their enemies. If one were to hold a Hell's gaze for longer than a minute, they'd be forced unconscious by the drain of energy.
She was born into a bloodline that has found a way to take control of one breed of wayward Aggressor Demon - the Criivestev. Something like a demonic, twisted Crawler, Criivestevs were numerous in the Unclaimed Territories, leeching off the filth of the destroyed lands. Highly territorial, it was rare to find more than one of these demons in an area - at least, with both of them still intact enough to be considered living. With Estev Demuus no longer in the living world, the powers of a Demon Mage were used to fuse an Amulet with the power to control the Criivestev. There were only three Amulets ever made, and the Amulets are enchanted in such a way that they require the offering of the blood of the wearer to even activate - and once activated, the Amulet can only be removed or damaged by the wearer. This allowed the Amulets to be permanently bound to the bloodline it was introduced to, as the Amulets could only be passed on 'willingly'.
Tanako used her Amulet to take control of one of the Criivestev, and now uses the Demon as a powerful 'familiar' of a sorts. It does her bidding, without question, and would sacrifice its own life for her safety. She gladly uses the Criivestev to kill, occasionally even using the Demon to hunt her meals for her, and fight her battles.
In her mind, the Demon would make a powerful ally beyond the Red, and one day she'll likely seek Slayer Training so that she can take her 'pet' beyond the Border to kill some Warriors.
Koyang is completely immune to Abilities. It is bonded to Tanako through the power of her Amulet, and cannot be affected by mind alterations or other psychic control. Even the call of Estev Demuus will hold no sway over it. It is able to walk on any surface, even the top of water, without gravity having any effect. A Criivestev, sometimes referred to as a Chaos Crawler, is a brutal killer, able to rend through just about anything with its many clawed limbs, and it can easily reach speeds other beings only dream about. They have a natural ability to sense danger before it strikes, and are covered in many sets of red eyes, making it impossible for enemies to sneak up on them. They tend to have mouths on the tops of their skulls instead of jaws, and food is generally wrapped up in impossibly sticky webbing before being consumed mostly whole. The armoured bodies of a Criivestev cannot be punctured by claws, and only seem weak against enchanted weapons or Graephs.
Criivestevs are fully immune to fire, and are masters of pyromancy. They reproduce by spilling their own blood - with thousands of smaller Criivestev 'hatching' from the blood. When they are young, they appear like normal crawlers, but shortly after hatching they begin to mutate. It takes them about two weeks time to reach the size of an adult Criivestev, and they tend to be cannibalistic towards their own, so Criivestev tend to dislike their own offspring greatly.