Conversation so far:
What is Hush?
Batman: Hush is an American comic book story arc published by DC Comics featuring the superhero Batman.
What is the role of the Riddler in this story?
Riddler uses one of Ra's al Ghul's Lazarus Pits to cure himself
How does this change Riddler's life?
During the psychotic break that follows exposure to the Lazarus Pit, the Riddler deduces Batman's secret identity
Does Dr. Thomas Elliot accept Riddler's help?
Yes
Does Dr. Thomas Elliot's mother die?
No

Question: Why does he want to get revenge?
Self-contained rewrite: Why does Riddler want to get revenge?