The word that can substitute the given group of words "A person who is indifferent to pain and pleasures of life" is "Stoic."

Explanation of the options:

☀ Vagabond: This word refers to a person who wanders from place to place without a permanent home or job.

☀ Amateur: This word refers to a person who engages in an activity or pursuit for pleasure or as a hobby, rather than as a professional.

☀ Stoic: This word refers to a person who is indifferent to or unaffected by pleasure or pain, and who shows self-control, endurance, and resilience in the face of adversity.

☀ Recluse: This word refers to a person who lives in seclusion or isolation from society.