Interesting. Apparently Gaja's attack using Ultimate Magic was "immune" to Megicula's spell. I remember Patry used Ultimate Magic on Zagred and it had no effect at all but maybe the mix of using his life force, plus True Magic and Ultimate Magic it managed to cause some damage to Megicula but even if Gaja couldn't cause damage, Ultimate Magic could be the key to at least Noelle being able to protect Rill, Charlotte and herself. In short, I'm not sure but Gaja's sacrifice may have served to know that Ultimate Magic works vs Decaying World. When Noelle attacked Megicula she wasn't even using True Magic and Ultimate Magic that why Sea Dragon's Roar was vanished.
EDIT: I correct myself. Licht was the one who used Ultimate Magic against Zegred and managed to cause him damage by reducing it to only his heart. Maybe Gaja managed to do the same in his last attack. If he succeeded to create that opening, then the sword in Sacred Mode could kill Megicula. Noelle was trying to summon her sword again. We'll see what happens.
She was trying to summon only her sword again and it's the same one she used against Vanika. She will probably not be able to transform again but that doesn't mean she can't try to summon even one part of the weapon to mortally harm Megi.
In one of the panels you can see part of the weapon that Noelle is trying to summon again. Sacred Mode is the only way Noelle can kill Megicula and that sword contains that kind of magic.
Noelle is angry and has no time to waste using magic that won't kill Megicula because Vanika and Lolo are dying and if they die all is lost. At the moment the only option Noelle has is try to kill Megicula with the sword but for that she has to have a chance. And maybe that opportunity was given by Gaja with his attack. Maybe he managed to expose Megicula's heart. This is why it makes sense that Noelle is trying to summon the sword again.
Noelle learned True Magic (and I think Ultimate Magic too) and that magic uses the mana of nature allowing you theoretically not to run out of mana but that alone can't harm a devil but she could defend herself and protect her comrades because Noelle also has very strong defensive spells and maybe can also use her Valkyrie armor.
I'm pretty sure 90% of the people who say Noelle is a tsundere have only seen the anime. In the anime they made up a lot of her attitudes such as the times she punch Asta (in the manga it happens only twice in almost 300 chapters and it was because she was embarresed of her feelings for Asta). Its true that at the beginning she had a cold and a distant attitude but that was because she was raised to hate everyone who was not royalty and that was also a mask to hide her own insecurities but once she began to know the Black Bulls and the rest of the world those prejudices disappeared. Noelle always cared for her comrades and would give her life for them. Think twice before saying that she is a tsundere because she never was.
Only two chapters left, I think.
Stop playing ☹
I'm not playing.
Stop joking around then