- A mask hides the face, but frees the soul. A mask speaks the truth.
- — Richard Sionis src
Richard Sionis, to the average person, is the owner of a successful financial firm with an office filled with historical masks, his interest. However, Sionis is secretly the operator of an underground fighting arena, forcing some of his employees to fight in an office building against their wills.
When Det. Jim Gordon began to investigate the death of one of the unlucky fighters, his investigations lead him to Sionis, who kept his cool as the officers questioned him. While he investigated further into the case, Sionis captured Gordon and forced him to fight in the arena against the other detainees. Gordon defeated his opponents and was eventually pitted against Sionis himself, wearing a black warrior's mask and wielding a sword. Again, Gordon beat his aggressor and arrested him. 
Sionis was later broken out of Arkham Asylum along with other fellow prisoners by Theo Galavan. Theo wanted to create a team of villains to cause chaos and destruction in Gotham City. However Sionis turned down the proposal, which led to being then strangled and then stabbed to death by Theo's sister Tabitha.
- The Mask was portrayed by Todd Stashwick.
- Richard Sionis shares the same surname and a similar alias and mask to Roman Sionis, a supervillain in the comics known as Black Mask.
- 2 Appearances of Richard Sionis (Gotham)
- 3 Images featuring Richard Sionis (Gotham)
- 1 Quotations by or about Richard Sionis (Gotham)
- Character Gallery: Richard Sionis (Gotham)