Soul Swap
At the completion of the chant, you draw the target's soul from its body, placing it within the gem (or similar object). With a quick word of release, your soul then exits your body and takes residence within the target's body, your body falling lifeless to the ground in a Comatose state. It will die in 1d4 days unless a soul or spirit possesses the body before then. Your body may be maintained for longer through a Gentle Repose ritual or similar ability. At your option, you may then transfer the target's soul into your own body, removing it from the object.
Once you are within the target's body, you can control the body as if it were your own. You maintain all your original statistics and abilities, except that you have the Physical Attributes (i.e. Strength, Dexterity, and Constitution) and Racial Features of the target's body. Similarly, if you place the target's soul in your body, it will maintain its original statistics and abilities, but take on your body's Physical Attributes and Racial Features.
You and the target maintain these new states until you (or someone else) performs this ritual a second time to reverse the effects. Your body must be intact (i.e. not decomposing) in order to return your soul to its body. Likewise the object containing the target's soul must remain intact, or the target's soul dies. If the object remains intact, the target's soul can survive within it indefinitely. If your are killed while within the target's body, you die. Similarly if the target dies while within your body, it dies.
At your option, a willing creature may take your place in this ritual, taking over the body of the target in your stead. When they do so, it is the willing creature's body that begins to die and decompose if the target's soul is not transferred within.