The word 'psychopomp' is derived from Greek and means 'leader of souls'. 

The shaman assists a person who has died to cross over to the Light. For a variety of reasons, some individuals remain earthbound after death instead of crossing over into the Light. 

Some situations which cause an individual's spirit to remain on earth after death include, a sudden and unexpected death (including murder, death through war, an accident or suicide), or a deep attachment to a person or family or a strong desire to complete some remaining unfinished business. 

A shaman's job is to help that individual soul move out of this dimension upon death, and take it to the Light.