Campaign Creations

Hello, I need again your help.
I'm on chapter 5 of Book 4, I think I did everything in the map except killing Metallus, but there is still one undiscovered side quest in my quests menu. I did the Gorbash side quest and the Vektra side quest (the one where I had to destroy 5 Juggernauts), but I cannot find the third one. Is it the Siege Machines quest listed in the secrets section of the website or something else?
And regarding that secret, in the website I read that to obtain it I must fail to protect the Zande against the siege machines in chapter 1, but when I played that chapter there wasn't any attack including siege machines. Maybe it's the Eclipse Cannon attack? Or the siege ramp side quest? Or something else?
Thanks for your help.

It is the Siege Machine side quest, and yeah, you have to fail to stop the Siege Ramp in order to unlock it.

Don't worry about it so much, it's mostly there to stroke Abolisher's ego.

Thanks!