The Transmigration skill is used to release trapped spirits from soul gems. Transmigration is a class skill available to the Shaman class it may or may not be available to other classes via item bonuses.
Releasing a spirit from a soul gem causes a new monster to spawn which can then be killed.
Skill Use
To release a spirit from a soul gem go to your Inventory click on the Soul Gem you wish to release and then click the use button.
The transmigrate screen is then shown which provides you with easy access to all your held soul gems for the purpose of releasing the spirits.
If you have enough skill to use a soul gem click on it and click the Release button.
Please note the soul gem is destroyed although you can kill the monster you spawn and soul trap it again if you so wish.
Souls are released to the tile you are on which means if you release a soul gem while standing in a building room the soul will be released to the tile.
Tiles that have monster spawns turned off can not be released to but all other tiles can be.
You will receive a purple skill gain and experience for releasing a soul gem in this way.
Formula
Transmigration required = (Soul Gem Level * 5)
i.e. To release a level 50 soul gem you will need 250 transmigration skill.