- "Tell you what, I take his head, and you can have the rest of him!"
- —Sykes to Ramos Silva about Jim Gordon[src]
No Man's Land
He and his gang kidnapped children by murdering their parents to make them work. The Soothsayers planned to dig a tunnel under the Gotham River in order to reach the mainland.
No Man's Land: Day 88
When the GCPD came for help, Sykes and his gang attacked Captain Gordon. When the gang managed to corner Gordon and Harvey Bullock outside of Mother's lair, they fought over them with Ramos Silva and her gang. When the two gangs were preparing to fight, Jim shot Silva in the head, shortly followed by Barbara Kean, who entered the scene in a monster truck and gunned down the entirety of the two gangs. Sykes later attempted to shoot Barbara, but was swiftly shot by Jim.
Sykes later appears alive and well and it is revealed that he and his men are working for Jeremiah Valeska, who kills Sykes by slashing his throat when he protests how Jeremiah is making his men work. 
Sykes appeared to be an extremely emotionally unstable man, losing his temper at any little annoyance. He does have compassion for his men though as he attempted to stick up for them to Jeremiah Valeska. Something that cost him his life.