<span>they liked to go and explore the psychological effects of sin and madness and also derangement of the human psyche.
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A valetudinarian is a <span>character in weak stamina or sickly, particularly an individual who is continually preoccupied with their case of fitness.
Wow that's a HUGE word ;D
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Answer:
I believe it would be 'self.'
Please let me know if I'm wrong!