ThunderCats (comics) entered the Book of Omens to begin his training and claim his rightful place as Lord of the ThunderCats, but Mumm-Ra uses a powerful spell to keep Lion-O trapped in the book for several years in real time, not "Book" time, and seizes control of Thundera afterwards. In the follow-up mini-series, "The Return" (written by Gilmore and illustrated by Benes, Pimental and Lea), published in 2003, Lion-O returned to Thundera to find it enslaved to Mumm-Ra. Several of the ThunderCats are scattered. Panthro, who was left in charge while Lion-O was away, was forced into slave labor. Tygra and Cheetara
He-Man/ThunderCats illusion any longer, and Castle Grayskull is revealed in front of the final Spirit. The Spirit attacks the Castle and the Sorceress manages to hold a protective shield to keep the Castle safe. Panthro and Man-At-Arms aim the cannon at the Spirit and fire, knocking it back. Before they can fire again the Spirit grabs Man-At-Arms and Panthro leaps to free him. While the Spirit is distracted by the two Tygra manages to aim the cannon at the Disk and fire, destroying the last Spirit. As the heroes celebrate, Skeletor watches and comments to Mumm-Ra that the Spirits did better