Nobody was more surprised than Will to find out Nico could draw- and not stick figures like Percy, but impressive works of art, filled with so much detail it could have been real.

The first time Will saw Nico's artwork after a nightmare, he almost dropped the sketch book- inside on every other page were drawings of Tartarus, drawn in such detail that he felt he was there, and that scared him.

If he was scared just by looking at it, how did Nico, Percy or Annabeth feel actually being there?