Approach the end boss in 'Abaddon's Gate' (the final mission in Nightfall) without provoking hostility in any way and and type '/dance'. When your entire party has also done this the end boss will begin dancing as well and when he completes his dance will kill your entire party with a message that 'You got served!'.
In the Jokanur Diggings mission, if you and your party die on the third trial (the Trial of Preservance)unless Kormir dies, don't click go back to town. If the spirit you're trying to protect actually makes it to the podium, it goes to a cutscene and resurects you