Nova is a new feature that gives you a one time use AOE attack per mission. When you get into combat, you’ll find the button on the right side, as shown below:

If you hit that button, it will perform the attack. When you fight the next enemy in the same mission, the button is no longer there:

This adds an element of strategy to using Nova - specifically, you want to use it against the strongest enemies in the stage and usually in groups. This is where you’ll get the most benefit.
Nova damage is very special because it isn’t affected very strongly by enemy level. Often, if an enemy is a high level it has high defense. This makes normal attacks and sometimes non-buffed special attacks do no damage. It’s annoying in Coliseum and High Score Challenges when you just need that one little hit left and you don’t want to waste Special bars to get it! But where a 10k attack with a medal might get turned into 1 damage at high level enemies, a 10k Nova does not. It is very reliable damage.
Nova damage is also calculated as non-attribute damage. It can be buffed by strength up medals such as Pooh, Piglet, and Illustrated Kairi. It can also be buffed by defense down medals like Mr. Smee and Megara. However, Nova damage is not affected by type-strength or type-defense: no Jack&Sally, Illustrated Black Coat Mickey, or Sora&Donald&Goofy.
For example:
Nova: 28,384 damage
iKairi + Nova: 45,821 damage
iKairi + J&S + Nova: 45,821 damage
Lastly, Nova can be leveled up. Each unique medal that you have guilted will give 1 level to your nova, and each unique medal that is at its maximum guilt will give 5 levels to your nova. This is sometimes hard to keep track of, but luckily the Album is updated to keep track of it for you:

The empty circle next to 6* Riku shows it has not been guilted and has contributed 0 levels to Nova.
The bright circle next to 6* Goofy shows it has been guilted to maximum (50% in this case) and has contributed 6 levels to Nova. One for guilting, five for maximum.
The dim circle next to 6* Mushu shows it has been guilted, but not to maximum (42% rather than 50%) and has contributed 1 level to Nova.
My Nova level is at 154, meaning I have guilted 49 medals, with 21 at max guilt. 21x5=105+49=154.
Leveling up your Nova gives it more damage.
Lv. 42: ~10,000
Lv. 61: ~13,000
Lv. 154: ~28,000
The general consensus is that with +3 Strength, Nova goes up ~25k per 100 levels.
However, you can only get this bonus from each medal ONE TIME. That is, if you guilt Mushu twice, you only get one Nova level. If you get two Mushus to 50%, you still only get 5 levels, not 10. I have two 100% Meowjestys, but I only got 6 levels, not 12.
Once you get the Nova bonus, you keep it forever. You can sell the medal if you want and you won’t lose any Nova levels.
Now there are a couple obvious ways to get your Nova level up, so let’s do a quick run down:
1.) Farmables. You can do story missions to endlessly guilt and reroll. There are 15 farmables, which is 90 levels of Nova! The best part is, you don’t have to waste any magic mirrors if you have the patience and luck.
2.) Events. Often there are events such as the Jungle Book one or the Meow Wow one where they give you an infinite number of a single medal. Getting those medals guilted and rerolled is a great way to boost your Nova.
3.) Save everything. It might seem trivial to keep Dumbo around, but when you pull your fifteenth one you might regret selling them! I actually have a 100% guilted Megara - though it serves no practical purpose - because I held onto multiples.
4.) Magic Mirrors. They can tip your 98% rolls into 100%. Don’t spend 20 MM just for five Nova levels though! Spend your MM on medals you will actually use! I would use no more than three or four MM on a medal you won’t use - for instance, I used three MM on my Megara. But I wouldn’t use 8 MM to get Mushu for 42% to 50%.
5.) Wait until Guilt Events, when minimum guilt rolls are much higher. This isn’t important for T1 Farmables, but T2, T3, etc. are limited chances. And the higher you roll for guilt, the less Mirrors you need to get the extra 5 levels from Max Guilt.
Remember: Nova is great. It’s an amazing advantage and a great new strategic attack. But investing your resources - specifically Magic Mirrors - into Nova over something useful (like Marluxia B) actually puts you at a disadvantage. Nova is a supplemental attack: it is not your main damage. You can only use it once per mission. Your medals come first.
Alright that’s everything I can think of! If anyone has comments or questions feel free to message me! I’m going to try putting up more guides like this in the future.
Thank you and good luck on those guilt rolls!!
<3 KCM

