From D&D Wiki
 Soul Split
A ritual to split a soul into two completely different bodies, or into a new body created specially for the ritual
|Level:||25||Component Cost:||100,000 gp, the ritual also requires a specifically designated target to have it's soul split, witch can be the caster or a willing or helpless individual.|
|Category:||Creation||Market Price:||500,000 gp, the ritual is outlawed in most kingdoms|
|Time:||Ten hours||Key Skill:||Arcana|
The soul split ritual is a ritual destined to take the soul of either the caster or an individual (Individual must be either willing or helpless) and split it into two parts. One half of the soul stays with the host body and remains under his/her control. The other half gets transferred into a dead corpse or a create a completely new body. This half soul now has a will of it's own.
The half soul can be given whatever form of personality, morals and thoughts the caster wants it to have when it is transferred. Usually, casters make the soul either exactly like the original, except in a new body, or the exact opposite. Such as, if you wanted, you (Or your captors) could make a 'Dark' version of yourself (A bit like Dark Link from Legend of Zelda). After the soul has been transferred and the ritual is done, the half soul becomes an independent being with a will of it's own. This means if you make a Dark version of yourself, it could very easily betray you.
If you transfer half of a soul into a corpse, the body reanimates and is now under control of the half soul. The personality is still the choice of the caster, but the soul is has the powers the the body's original owner had. This means if you cast it into a civilian's corpse, it makes the soul have all the ability of a normal civilian. This also means that if you cast it an Arch-Wizard's body, they have all his ability and spells at their disposal.
If you create a completely new body using the ritual, the body has all the abilities of the focus of the ritual. The new body looks exactly like the focus's body, except the caster can change the skin tone, hair color and eye color.
The created being has the same statics as the body it was given, or the focus's statics if a new body is created.
After the ritual, the focus can never be used as a focus for this ritual again. They're soul has already been halved, and cannot be halved again. Any attempts to half a soul again will automatically fail and kill the focus.