SeerTale

Soul Seers

ALRIGHT! Let's get some stuff covered:

Soul Seer: Soul Seers have strange abilities. They have only ever been monsters, marked by a soul of two colors, one main color and the second around the outside, and incurable blindness. Their first main ability is to sense other souls and 'read' them. This tells them what creature they are and if they can be trusted. They have three other main abilities based on their level, which grows with the practice of their magic, not their fighting: the Possess, Capture, and the Shield.
Possess allows a Soul Seer to, at LV 3, control the simple movements of a target and keep them in place for a small amount of time. A LV 5 Soul Seer is able to control the magic and weapons of anyone they use Possess on. For example: If a Soul Seer were to Possess any Sans(other than Swap), they could make the Sans use a Gaster Blaster on themselves, targets around them or the Soul Seer themself. Though, in general, Possess uses a lot of energy and will only last a few seconds.
Capture is gained at LV 7. It allows a user to magically chain a target for any amount of time and any distance away, as long as they remain awake. Say Chara arrives and starts killing monsters, a Soul Seer would be able to use Capture to either chain them to the ground or use Possess to make them drop the knife, then Capture to bound their hands and feet together until a royal guard may come to get them. This uses very little energy and can last for days, as long as the Soul Seer remains awake.
Sheild is earned at LV 11 and allows a Soul Seer to take an enemy's soul and turn it into a force field for a certain amount of hits depending on the enemy's HP and strength. This will kill the soul once that amount of hits has been taken, along with the enemy. Though Soul Seers cannot use their own soul or the soul of an ally, no matter how much anyone wishes they could. This is simple to use and drains energy, but not as fiercely as Possess does. Here is an example of each one:

A Soul Seer is stuck in a battle. They are able to sense their enemy's soul and dodge. There are three enemies. Sheild: The Soul Seer reaches out their hand. The soul of one enemy comes to their hand and the Soul Seer throws it to the ground like a bomb. It turns into a force field, surrounding the Soul Seer and their allies. The enemy whose soul was taken is unable to move, though the other two don't think it will affect the third and hit it until it gives way, dusting the unmoving enemy. Capture: The Soul Seer pushes its allies back and sweeps their hand in the direction of the next target. Magic chains wrap around their wrists and knees, forcing them to the ground and keeping them from fighting back. Possess: The Soul Seer calls the soul of the last enemy. They hold the soul and walk in the sensed direction of the chained enemy. The possessed enemy follows and the Soul Seer lifts their arm, making the enemy lift their weapon above the captured's head. They swiftly bring their arm down, making the possessed dust their ally. The Soul Seer squeezes the soul and crushes it, effectively dusting the possessed. After a second, their body catches up with how much energy has been used and they pass out.

And for those of you show would want to make a Soul Seer have a child:

Unlike other monsters, a Soul Seer's soul does not trade any part of itself with its soulmate's or children's, though they remain connected spiritually and can tell whether or not one is in danger and where. There is a 5% chance that the child of a Soul Seer will also be a Soul Seer. The only way to really tell is if the Soul Seer weakens during pregnancy and passes after childbirth. This is because there is only ever one Soul Seer at a time, though it is not determined whether or not there is always a Soul Seer somewhere in the world. Because of this, it will take much longer for Soul Seers to become pregnant, as their soul does not want to leave a blind child in the care of someone who would abuse them, and a cracked soul struggles much more to have a child, often causing miscarriages. This is because, when a soul seer's soul is cracked, the Soul Seer was either previously abused or still is and, like above, doesn't want any child in the care of someone like that. Male Soul Seers are more than likely to choose another male as a soul mate, as they are weaker and it is harder for a soul to tell if their child is a Soul Seer without carrying them itself.

Other info(I guess):

A Soul Seer's soul automatically heals itself, bringing up the seer's HP if they are injured. This is marked by whether or not the outside color of a Soul Seer's soul is glowing. Ex: If a Soul Seer has a magenta soul with blue around the edges, the blue will glow Cyan when healing.  They can also heal other monsters by holding their hand or something, kind of tricking the soul into thinking the seer's HP is low. A Soul Seer's soul is the soul of a monster, no matter if it belongs to a human or a monster. This means that, no matter what, a Soul Seer will not pass until they reach 0 HP and, once they do, they will turn to dust.

They also have the ability to "look through" souls, though it depends on the Soul Seer, so it has never been documented.  This is when they look through the memories of a monster or human, making the owner of the soul see the same the Soul Seer is.  A Soul Seer would be unable to use this to see, however, as it can only be memories that have been created at least a week prior.  They can't look through their own soul, but they can others.  If they really want, they can even manipulate memories.  This allows them to, if they want, torture others, though it is only needed if the royals have already been doing so for a while and the being still refuses to speak.  This is another reason why this ability has never been documented.