Old Hob, Slash, and their crew have become a force to be reckoned with, and, when someone close to the group is kidnapped, the Mutanimals end up on an adventure more wild and dangerous than they could ever have imagined. Then, the Turtles return from Burnow Island to find unimaginable tragedy. As the family struggles to cope, an enraged Foot Clan prepares its revenge. Meanwhile, Casey prepares for a final showdown with Hun as the Purple Dragons run amok, and April has come into possession of an ancient scroll that seems to point to answers regarding the Pantheon. It all leads to a final showdown as Karai decrees a Gauntlet battle between Splinter and Shredder.

Collects the Mutanimals mini-series by Paul Allor and Andy Kuhn; issues #45-50 of the ongoing series by Tom Waltz, Kevin Eastman, Mateus Santolouco, and Cory Smith; the 2015 Free Comic Book Day issue; and the Casey & April mini-series by Mariko Tamaki and Irene Koh.