Elusa's group invisibility illusion was already exquisite, and with the upgraded high-ranking equipment and Little Illusion's assistance, it was able to cover the five advancing legions in dense formation.
With the combined cooperation of the above three points, they managed to appear behind the enemy without anyone's knowledge.
"As for the attack on the eight enemy legions left behind at the entrance of the Galaxy Corridor, it was led by Ariel's sister, Third Princess of Coldflame, Caroline, along with Kingdom General Hilda, and 60,000 soldiers from the Northern Army, my Crystal Blue City Battle Puppet Regiment, and a combined legion of Defense Army from Firsdale City and Mystara City."
"At the start of the war, through Crystal Blue City's instant teleportation, Caroline and Hilda led their troops in hiding, always ready to strike."