Personal Info:
Real Name: Byron Meredith
Also Known As: Doctor Byron Merideth
Place Of Birth: Gotham City
First Appearance: Detective Comics Vol.2 #16 (2013) Modern Age Villain
Known Associates: Philip Miles, Annie McCloud, David "Happy" Hill
Group Affiliation: Leader of the League of Smiles
Base Of Operations: Gotham City
Grudges: Batman
Creators: John Layman and Jason Fabok
Merrymaker has no super human powers; however he is a trained psychiatrist and an expert amoral manipulator.
Dr. Byron Meredith was a former psychiatrist at Arkham Asylum. He was infamous for his violent ways of treating his patients. While most doctors feared the madness of The Joker, Meredith and Dr. Harleen Quinzel were the only ones willing to take on the Clown Prince of Crime. While Harleen later went mad with The Joker and became his girlfriend and sidekick; Dr. Meredith opened private practice for the Joker obsessed.
Soon he convinced his patients that it would make the Joker proud to cause chaos in Gotham but in reality he was using the chaos as a diversion so he could kill people who had wronged him. Dressing as the Merrymaker, he became the leader of the gang known as the League of Smiles
Merrymaker at Batman Wiki
Merrymaker at DC Database
Merrymaker at Comic Vine