Memento Mori, the Latin phrase meaning "Remember you will die," is a great description for the expansion that focuses on integrating learned skills and DNA directly into the character as they level. Previously, players would have to visit a trainer to learn skills, or assemble DNA strands with a DNA scientist in order to equip DNA mutations.
Now these two aspects of character development have been placed into the game as talent-esque windows, which allow you to spread your points amongst new upgrades the moment you level. It's almost like you're "remembering" your skills and DNA abilities instead of learning them. We appreciate that.
Memento Mori is also adding many more new items to the game, such as pets, new DNA, fast skill progression, and more. Now you can rip up your enemies with twice the ferocity and splashes of blood!
However, so much is being added with Memento Mori that we really don't have the room to describe it all here. If you want to check it out, the Requiem website has added a huge truckload on how the expansion impacts each and everyone of its classes, so flip on through and enjoy all of the info over there.