[looks down, then draws the knife out of his chest, bloodlessly. Or at least with no more blood than before. The blade is carved into a key shape, and he holds it out]

This is yours. Nobody else can have it—no matter who else is in and exploring my heart, they won't get this key. It belongs to you. I don't know what it unlocks, but I know it's something in Truth. I honestly don't know anything down there. I just know that there's a drop, and no going back from it but when you get to the end of Truth you can get out. There shouldn't be anything you have to solve down there because it's just... all Truth.