Okay, so the players try chopping off a head, say the red one, and the whispers start to dissipate (and no heads grow back). Awesome! they think, and quickly dispatch the other two. But once all three heads are gone, five more grow back: green, blue, red, white, and different red, I guess? And the party is immediately beset by visions, which are somewhat clearer and more vivid than the last ones.