The particular example I was shown involved stepping into the shoes of Laerdan, an Elf-Lord with whom players have interacted in previous quests. Whereas the story contained in those earlier questlines has led the player to believe that Laerdan has betrayed them, Elrond knows otherwise and "tells" the player his story. As the Elf-Lord, I adventured and fought my way through masses of enemies - thankfully possessing roughly 10 times the hit points of a standard LotRO character - trying to track down and rescue Laerdan's missing daughter. Along the way I encountered not only forces aligned with Sauron but Orcs bearing the White Hand of Saruman, a portent of things to come in the story of LotRO. While I won't spoil the conclusion of the story for players intent on experiencing it themselves, I thoroughly enjoyed my first taste of session play; more than that, I was excited for the possibilities when combined with the expansive lore of Tolkien's world.
Campbell explained that through tools such as session play, Turbine is trying to introduce new ways to tell the stories of Middle-earth to LotRO players with the launch of Moria. Another session play event they mentioned cast the player as an Angmarim Torturer, the minion of an adversary players faced back in Book 12. By allowing the player to literally see through the eyes of their enemy, Turbine hopes to give players who are invested in the story and the lore a better understanding of the War of the Ring. For all the rest, there's always phat lewt.
Session play offers Turbine an opportunity to explore Middle-earth in a way the current game simply doesn't allow. Laerdan's quest was essentially Elrond telling me his story - and from there, it's barely a jump to allowing players to experience other tales in Tolkien's mythology. Campbell let it slip that something they had been considering was allowing players to revisit the glory days of Moria recounted by Gimli.
A significant portion of the update - including the tale of Laerdan - focuses on Eregion, a land to the west of Moria that will play a prominent role in the expansion. Perhaps most significant amongst the features of Eregion are the Ring-Forges, the Elven furnaces in which all the magical Rings of Power were forged - save One. Now inhabited by a host of baddies, the Ring-Forges are Book 14's new proving ground, a dungeon for players to enter in the name of smiting the wicked (and taking their stuff).
Campbell and Mersky walked me through the beginning of the zone, including a boss fight against a particularly brutal Troll Gate Warden. Fortunately, despite the monster's crushing strength, we ultimately prevailed thanks to our admin powers. They led me a short way further into the Ring-Forges and showed me a particularly nice bit of flavor: "Beautiful Sauron."
This mural on the wall depicts Sauron not as the fearsome villain we know and loathe, but in the beautiful and elegant form he chose to assume after pretending to reform his ways - while deceiving the races of Middle-earth and forging the Rings of Power. Though the painting shows him as benevolent and surrounded by admiring elves, its presence was enough to inspire enough Dread that even my hardy Dwarf cowered in terror while we were near it.