When they sealed Insect Emperor Behemoth, it wasn't a decision they'd made on a whim. They had thought it through carefully.
God Emperor Athena had already considered the possibility that Insect Emperor Behemoth might cause too much trouble. If she did, Athena would enter the seal and make her behave.
The Light-Dark Seal inside the Light-Dark Psionic Seal could be reinforced by Medivh working together with the Seven Virtues and Seven Deadly Sins.
Even though Medivh was only a Half-Step God Emperor, with the Seven Virtues and Seven Deadly Sins supporting him, he was more than capable of stabilizing the seal.
They weren't expected to fight the Insect Emperor head-on, only to restrain her while Athena suppressed her.
After Medivh advanced to God Emperor, there would be even less to worry about.
Medivh knew Athena's Law of Light and Dark. By maintaining the Light-Dark Psionic Seal alongside Luna, he could do a better job than Athena and Luna working together.
After all, Athena and Luna couldn't coordinate perfectly.
Moreover, Medivh's Law of Desecration allowed him to steal others' power through desecration.
Medivh could also call upon Luna's Psionic Net.
When Insect Emperor Behemoth attacked the seal now, she was practically kicking an iron plate.
If Insect Emperor Behemoth put her face within reach, Medivh wouldn't hold back. He'd slap her hard several times, teaming up with Athena to hit her from both sides.
When Insect Emperor Behemoth realized that Medivh and Luna were guarding the seal, and that the Light-Dark Psionic Seal was even sturdier than before, she gave up struggling and waited for a better opportunity.
Once Insect Emperor Behemoth quieted down, Medivh continued desecrating Luna, stealing her divine office of the Psionic Net.
Insect Emperor Behemoth could take a beating. Medivh and Athena would have to attack her