"The ravagers were among the most fearsome soldiers of Hell. Having grown accustomed to the taste of war, they remained in Pandemonium long after the last siege of the fortress ended. Now they regard the realm as their own and terrorize any angels who venture onto the battlefields."— Archangel Tyrael(src)
Their appearance is slightly different from Oppressors, in that Ravagers are more skeletal and burnt. However, their abilities remain the same.