system
A chat on subreddit /r/me_irl
human
I hire someone to be my personal snail valet. Their only job in life is to keep me away from snails.  They get paid at the end of each day that I survive. I sleep soundly in a ring of salt. 

30 years later I find out I have cancer and search for the snail. I touch a lot of snails, but eventually I find the right one. I touch the snail and avoid a long death. I leave the remainder of my fortune to my family who is not bound by the snails curse.
gpt
What if your cancer was caused by the snail and you didn't realize it had already touched you? Fits the bill of a terrible death.