of Tsarist Russia, astral travel, out of body experiences and Stephen Hawking's theories on wormholes. Dailor has also said that "Crack the Skye" is meant as a homage to his sister, Skye Dailor, who committed suicide at age 14. Scott Kelly, who guested on the title track, has this to say about the song: Packaging Paul Romano, who had done all of Mastodon's album artwork to that point, created the art for Crack the Skye. The piece features various ethereal images tied in closely with the overall concept of the record. Crack the Skye was released in two editions: the standard and limited edition. The latter has an elaborate packaging with a tunnel book that, when looked through, reveals three-dimensional-like imagery. A "hidden" picture of Brann Dailor's sister, Skye, can be seen on both sides of the tunnel book as well. Release Crack the Skye has been released as standard CD version and CD/DVD version, which included a bonus DVD with a documentary and a track commentary. Furthermore, standard single-disc LP and limited-edition 2xLP were released. A "super-deluxe" CD/DVD version that includes a tunnel book and a lithograph of the album art sold out during pre-orders, and a "Royal Edition" with a CD of the instrumental versions of the songs and an entirely new black-and-gold artwork was released on December 15, 2009. Critical reception The initial critical response from music critics to Crack the Skye was very positive. At Metacritic, which assigns a normalized rating out of 100 to reviews from mainstream critics, the album has received a score of 82, based on 29 reviews, indicating "Universal Acclaim". Amongst the positive reviews received from critics was Total Guitar Nick Cracknell who awarded the album a 5/5 rating, describing it as "even more ambitious in scope and sound than 2006's Blood Mountain. Embracing elements of prog and country, but above all classic rock, Hinds and Kelliher literally add new dimensions to the band's ever-expanding sound." Decibel, who named Blood Mountain as their number 1 album of 2006, gave Crack the Skye a 7/10 rating as reviewer Joe Gross responded that "Crack is clearly designed as a grower, not a shower, the sound of a band that grew tired of people not responding to their ground game, so they put the ball in the air. Who knows when it will come down?" Clash review was particularly glowing in its praise for the