It should be mentioned that Wilkie Collins was a "notorious opium-eater" himself. The Colonel may be an allusion to himself, and the negative way in which he is depicted could be interpreted as Collins' self-loathing.

The curse of the Diamond itself may be an allegory for the corrupting influence of opium addiction. The "wretched crystal" that he "picked up" in India can be construed as a metaphor for a bad drug habit.