Gadra/Chronology

Eve of War Arc
Before the Empire began its invasion, he sent Shinji Tanimura, Mark Lauren, and Zhen to Tempest as spies. Meanwhile, he personally travelled to the Farmenas Kingdom, intending to convince Razen to submit to the Empire. Much to his surprise, he learned that his subjects of revenge were eliminated, and Tempest turned out to be much more powerful than he expected.

Judging the Eastern Empire's invasion to be a lost cause, he defected to Tempest alongside Shinji and his team, and has been given the guest treatment since. Gadra ended up as the new guardian of the 60th floor in The Dungeon and became a hidden boss besides the Demon Colossus.