Holding aloft your spirit prison with a freshly cut hand you make a ranged attack to fire a light purple “tractor beam” (range 60ft) which captures the spirit of the target creature and draws it 10ft towards you once upon casting and at each start of your turn. At the start of each of the creature’s turn they may make a CON save to break free. If they succeed they take 10d10 psychic damage but regain their spirit. If the target has a physical body they may only use their turn to also attempt moving half their movement speed leaving their spirit behind and taking 1d10 psychic damage (otherwise the creature is unable to do anything but attempt a save). If the target takes damage, is ever in total cover, or their body moves out of range, the spell ends and the target takes 10d10 psychic damage regaining their spirit. For the duration of the spell the beam requires concentration and consumes all of the wielder's actions while still free to move. If the spirit is drawn all the way to the prison at the start of the wielder’s turn, it is captured and the associated body (if it has one) falls dead to the ground. This spell does nothing to creatures without a spirit such as constructs and many undead. 

Once Captured:

When a spirit is captured in their amethyst prison it is keyed to the caster's blood, and no other spirit may be captured with it nor can it be used by another caster. 

The spirit is locked in the prison indefinitely and can not be returned to life except by a wish spell (shattering the gem). If the prison is destroyed the spirit is freed to pass on to the afterlife.

Alternatively one action may be taken to drip the caster's blood on the prison and release the spirit as a wraith (leaving the prison empty for reuse). When released the wraith's primary desire is to find its body and reinhabit it (if possible, or otherwise wander for eternity). It is unfriendly toward you and your companions. Roll initiative for the wraith, which has its own turns. It is under the Dungeon Master’s control and acts according to its nature on each of its turns, which might result in it attacking you if it thinks it can prevail. You may attempt a CHA 17 check (or any flavorful check the DM deems appropriate) to convince it to help you in your purposes. On a success it will work with you for as long as it sees fit, but will become hostile if you or a companion attacks it. The DM has the creature’s statistics.