Emet-Selch secretly made a memory crystal commemorating Azem, the PC's Ancient incarnation from the days of Amaurot, and imbued it with Azem's signature magic of summoning like-minded individuals from across space and time. When banished to the Rift by Elidibus, the PC used it to call on Emet's not-totally-dissolved-in-the-Lifestream soul to bail them out.

Fandaniel speculated that Emet may have "... found a way" to do something implicitly with memories, when Zenos mentions his dreams of the Final Days in the 5.2 stinger, I believe? It's really vague what he was talking about, in EN at least.