Moray Eel

As story goes, some centuries ago,
There lived magician's assistant
The aptest pupil he had soon to go
To arabs, where the schools are distant!
He learned so hard and tried to figure
Why people had to die so fast
The mystery of Death he was so eager
To own, and healing was his lust
You see me at the end of bed
Then you can save the poor lad
When at the heads i'm standing still
Don't even try, i'll break the deal!
As years passed by he saved the ill
Not hundreds but tenth more