There are 10 Riddler Trials in Batman Arkham Knight. Completing all of them will earn you the following trophies / achievements:
The Road to Hell [Bronze/ 10G]
Pieces of the Puzzle [Bronze / 10G]
The Cat and the Bat [Bronze / 10G]
Riddler on the Rampage [Bronze / 10G]
The Burning Question [Bronze / 10G]
The Primal Riddle [Bronze / 10G]
Death by Design [Bronze / 10G]
The Riddle Factory [Bronze / 10G]
Lethal Pursuits [Bronze / 10G]
Nine Lives [Bronze / 10G]
Riddle Me That [Silver / 30G]
They are all part of
آی-ویدئو