Soul Core is targeted the same as regular core by removal effects. The owner of a spirit being targeted by core removal can choose which core are moved. In addition, during the main step, spirits with only one core can switch core simultaneously between them without being depleted.
Q1. What is Soul Core?
A1. It is a special core which you may only have one of per game. It can be put onto spirits and used to pay cost to activate various effects.
Q2. Must Soul Core be used?
A2. You may choose whether to use it or not. If you do not, place one regular core to the reserve instead of Soul Core when setting up the game.
Q3. Can Soul Core be put onto spirits and used to pay cost like regular core?
A3. Yes, it can be.
Q4. Can Soul Core be moved by Awaken and "core moving effects"?
A4. Yes, it can be.
Q5. Can Soul Core be moved by "place one core to the void" and "place one core to your life" effects?
A5. No, it cannot be. Soul Core cannot be moved to the void or life during the game.
Note: as of April 1, 2016, Soul Core can be moved to the life through use of Seal.
Q6. Can core be switched between a spirit with only Soul Core on it and a spirit with one core?
A6. On your main step, core can be switched.
Q7. What happens when the opponent uses an effect that sends two core on a spirit to the void on your spirit with one Soul Core and one regular core?
A7. Soul Core cannot be sent to the void, so the regular core is sent to the void, and your spirit is not depleted.
Q8. Does the opponent choose which core to send to the trash when using an effect that sends one core on a spirit to the trash on your spirit with one Soul Core and one regular core?
A8. No, you choose. Even if it is the opponent's effect, you choose which core is moved to the trash.
Q9. Can a spirit with only Soul Core on it activate an effect that requires sending Soul Core from itself to the trash?
A9. No, if the spirit that activated the effect is depleted by sending Soul Core to the trash, that effect does not activate.
Q10. Do effects stating "if Soul Core was used to pay the summon cost" activate when Soul Core is placed to the trash when paying the summon cost?
A10. Yes, that is correct.
Q11. Can effects stating "if Soul Core was used to pay the summon cost" activate by placing Soul Core to the trash even when the summon cost becomes 0 due to reduction?
A11. No, they cannot. You cannot pay extra cost for summoning.
Q12. Can a cost 6 spirit with one Soul Core and one regular core be used for "Tribute: A cost of 6 or more -> Void"?
A12. No, it cannot. Tribute cannot be done if all of the core from the spirit is not moved to the void.