"Gray hand" or "dead hand" is an unofficial name for doctors whose treatment (by accident or by malicious intent) led to the death. This leaves an imprint on the doctor and he himself needs to undergo treatment. Also he is removed from working with people. In future, he is even forbidden to appear in public places without tight gloves since any accidental touch can harm others.
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I found a pic from 2017 and finally finished it. This year, Hans Kellyo has already turned 8 years old as a character and he still holds a leading position as "the most badass character".