My knowledge..
As I seem to recall, it is greek for “All Powers”. A combination of wrestling and boxing already practiced as sports by the ancient Greeks. Pankration was added to the Olympic Games in 648 B.C. In order to force his/her opponents to concede defeat, the Pankration artist uses punches, kicks, grabs, throws, joint-locks, and chokes. Ground fighting is a large part of their training.
Because Alexander the Great’s armies carried the sport with them across the Alps into Asia, too, and greek authorities still spout some claims that many asian grappling techniques are based on Pankration. Nothing confirmed though.
That’s about all the hearsay I got. However, I had the pleasure of sparring with a Pankration artist, as there is a school over here that teaches submission wrestling, Boxing and a little Pankration. I almost had him in the start with parries by the bucket-load and rapid punch combinations (I had been training a lot of Nan Ching then, and that was what I used mainly), and he tried to grapple with me for wrist and headlock takedowns. Then he started punching as well, and cold knocked me before putting me in an, quite agonizing, Ankle lock 
So, it’s mainly a lot of takedowns and joint locks, with added punch. Trust me, when they suddenly throw the punch, it has a great surprise value. But there it is, never assume you got someone’s style figured out 
Peace out, and I hope it helped,
Seeker of the Way.
The dance of life, the capering of elements, and skip of gods. The dance is mine, I AM the dance.