I was first introduced to Tool's debut full-length album when I was in junior high. A friend of mine brought a copy of the album in to school to lend to me, and at the time I was not familiar with Tool's music at all, let alone this particular release. Even before I took the CD home and was wowed by the dark, grimy metal, I was totally affected by the artwork.
Nearly every aspect of the art from Undertow is unsettling. From the pictures of the band members with pins stuck into their heads, to the naked people embracing inside the booklet, to the "secret" picture found under the CD tray, the artistic theme of the album is incredibly dark, with most of the pictures washed in a deep sepia tone. The obvious centerpiece visually for this album is the bright red, stylized ribcage found on the cover. While looking at the booklet, one's eye is constantly drawn back to the cover because the red is the brightest color in the entire pallet, and the ribs seem (to me, at least) to be groping to embrace you, and there is something imperceptibly unnerving about that.