Lyra thinks Discord is an idiot for not thinking to dodge when the Elements of Harmony were about to strike him. Discord thinks this is the perfect opportunity for a game.
How would a being like Discord want to be remembered after he's gone? Well, if you're curious, he did actually write a will. To the surprise of nobody, its contents are bizarre and mildly disturbing.
So what is the deal with all these humans who go to the Everfree Forest and fight manticores anyway? Well sit down, kids, and let grandpa tell you the whole story.