The illusory truth effect is the tendency for any statement that is repeated frequently—whether it is factually true or not, whether it is even plausible or not—to acquire the ring of truth.

After you get your hands on Slayer's Fang, you can start to uncover a set of illusory anchors in the mirror realm. Break these with Slayer's Fang, and you'll unlock new catalyst perks for this weapon.