Hero, Class and Skills FAQ and Errata

Q: What happens if the Shadow Soul is on the map when the Shadow Walker uses a skill that instructs him to place the Shadow Soul on the map?
A: The Shadow Soul is removed from its current location and placed as instructed.
Source: Official Errata

Q: When the Shadow Walker uses 'Soul Bound,' when exactly is the Shadow Soul placed?
A: The Shadow Soul is placed after resolving all the steps of combat that may cause the attack to be a miss. This is usually after the Shadow Walker rolls dice and checks range, but may happen during a later point of the attack if it is still not determined if the attack is a miss or not (such as needing to spend 1 g for the shadow dragon's 'Shadow' ability).
Source: Official Errata