The way I unbound souls is through this ritual:
-altar of shadows (must be made by a shadow realm Forge master)
-dagger of separation spell
-sigil of souls pendant (empty)
-6 people (person being unbound, ritual performer, 4 protection chanters)
First place the runes in their respective positions. Have the person being unbound lay on the altar with their head pointing at the life rune and their feet at the death rune. The ritual performer should then cast the spell to obtain the dagger. Have the 4 protection chanters stand at the designated points on the casting platform and chant:
"proteggere questi dèi onnipotenti anima"
Then the ritual performer should say:
"dal potere del legato arcaeus quest'anima e farla diventare immortale"
Then stab the person being unbound in the heart with the dagger of separation (don't worry the dagger is astral not physical so it won't harm anyone) when the resulting energy transfer has finished remove the dagger. The person's soul should now be unbound making them immortal (unless banished. They would go to the shadow realm if banished)
p.s. the shadow realm I am talking about is the one I created. To enter it you have to be apart of the order of shadows I started. Questions? Just ask.