The Talons are elite superhuman assassins who serve a 400 year old criminal secret-society called the Court of Owls. The Talons are raised from childhood to be perfect fighters and given special Electrum implants which give them superhuman healing abilities with their only weakness being cold temperatures.
William Cobb was one of the Court's chief assassins and the great-grandfather of Dick Grayson. He was an orphaned street-performer and pick-pocket in Gotham City who was taken into Haly's Circus. In the circus, he performed dangerous feats and became something of a celebrity for the time.
This eventually lead to him becoming hired to be a Talon for the Court of Owls where he was given an electrum implant which made him next to immortal.
Official LEGO Description
A group of lethal superhumans who serve the Court of Owls™, Talon Assassins™ are virtually unstoppable, as they are reanimated from death and able to withstand the most brutal punishment. The highly trained Talon Assassins are experts with knives and skilled in hand-to-hand combat. They are masters of stealth and concealment, which helps them to remain undetected. Moving through hidden catacombs beneath GOTHAM CITY™, they can easily attack Batman™ and disappear without a trace.