This can be done with the Sword and Shield. And can be obtained on your first or subsequent playthroughs.
1. Ensure Stamina Bar is full (Blue Bar) either by not fighting Faiz Tilus' or by retrieving the sacrifice.
2. Access central room where your are surrounded by the seven rocks.
3. Perform 10 light attacks (x) in a straight line.
If you mash the (x) button your character will only perform 9 attacks. After your character attacks with the shield there is usually a 1 second gap to continue a consecutive chain. So just pace your strikes.
Heavy attacks (y) require more stamina so avoid these.
Hope this Helps