S1·E20 The Unbelievable Truth About the Legendary Magic Knights

The girls head to the castle where a girl, looking like Princess Emeraude is waiting for them.

After mentioning Zagato's name, she goes berzerk, and climbs into her own machine. She starts to attack them, and they fly out of there (the girls are in their machines.)

Once outside, they start to get into a battle with the machine, and get the truth from Princess Emeraude, saying it's her.

She then tells them, how her sorta love affair (falling for Zagato actually) was a big no-no for the pillar who watched over Cephiro, and imprisioned herself so that feelings wouldn't get in the way.

It was too late for that, and she reveals inorder to save their land, and fulfill her wish, they would have to kill her!

She then reveals no one from Cephiro or suicide couldn't kill her, so that's why she summonded them. After attacking them, the girls combine into one machine, kill and proceeds to kill her. The huge light appears, and we see Princess Emeraude and Zagato together.