Restore the broken riftstone and stay put a bit to recover your pawns’ health. When ready, head to the arena. Here, you'll fight a living armor. The only way to deal considerable damage to this enemy is by attacking it at the back. It's attacks are solid but slow so just keep away from it when it starts brandishing its weapon. It's pretty resilient against magic attacks and can also knock down your characters easily.
After defeating it, collect the loot in the area and head to the exit. Here you'll find the last recollection tablet in the game. If you have the notice board quest “Echoes from Beyond” and if you followed this guide, you should be able to collect all recollections up to this point and complete the quest.