Before Zarkon can teach his son a harder lesson, Haggar intervenes and, after getting Lotor to beg for mercy for sake of his life, changes the subject to that of her new Robeast. You know, the latest one that will SURELY defeat voltron (this is where you go "duh-duh-DUN!1!!")
On Arus, the folks at the Castle notice the approaching Doom fleet and so try to send out some defensive satellites. Of course, they're easily destroyed. But at least it bought the VF time to launch the Lions. The new Robeast is launched almost immediately with a fierce battle ensuing. It's pretty obvious the Lions are no match (why do they even try? lol), so Voltron is formed - in an interesting sidenote, the Robeast does try to prevent Voltron's formation but is driven back by all the energy surrounding the Lions.
The blue Lion ends up taking a direct hit from two missiles however, which knocks Allura out of her seat and sends Voltron falling toward Arus' atmosphere (This is where Princess should say "They set us up the bomb!")
Voltron lands on a village and the Robeast follows to continue the fight while frightened villagers run for their lives. Voltron takes on some heavy damage, including more to the Blue Lion before old Volty finally gets the upper hand (helps when that hand has the blazing sword in it lol). But the drama's not over yet, folks.
Blue Lion is so badly damaged it falls out of formation with Voltron and crashes. Lotor orders it attacked, so the others quickly separate to protect it and the Princess inside. Luckily, Coran is able to drive off Lotor with a little help from the Castle's firepower. Afterwards, the Princess' injuries are tended to and Blue Lion undergoes extensive repairs. The bad guys may have lost again, but the good guys took a decent beating.