Backstabbed in a Backwater Dungeon: Volume 6 (Light Novel) by Meikyou Shisui

The Masters hosted by the Dragonute Empire have grown increasingly concerned about their lack of knowledge surrounding the emergence of the Great Tower as well as the sudden disappearances of former members of the Concord of the Tribes, so they hatch a scheme to find out who exactly they are up against. Their plan is to get the Beastfolk Federation to declare war on the Great Tower while they watch on from afar to learn about their opponents without the need to reveal themselves. For their part, the beastfolk have their own reasons for going to war with the Great Tower. Light’s lieutenant, Ellie—aka the Wicked Witch of the Tower—has successfully conquered the elves and the dark elves, freeing the human slaves suffering under their heels in the process. Not wishing to share the same fate, the beastfolk are determined to destroy the Great Tower. But how can a relatively weak nation fight a sorceress who has her own personal army of dragons? By fighting dirty, that’s how.