One of the defining parts of Grandia II's battle system are its use of the Mana Egg system. These eggs are the source of magical abilities used in and also outside of combat. Each one has a different combination of spells, some that can only be found on one specific egg. I decided to compile a list of mana eggs here, especially as there are optional eggs that can be missed.

Holy Egg

This is the first egg you will encounter in the game due to the fact that it is equipped to Elena when you first begin their journey together. This egg does not contain many offensive spells, but is one of the most useful eggs for healing in the game and also includes helpful buffing spells.

(Fire/Wind/Lightning, Demonic Mana Egg)

This egg is automatically equipped to Millenia when she joins your party. If Millenia leaves the party, make sure you equip it to another member in the mean time. This egg contains some of the most powerful offensive abilities in the game in contrast to Elena's Holy Egg. It also has a couple of helpful debuffing spells to weaken your enemies in battle.

Mist Egg

(Wind/Water/Blizzard, Airy Mana Egg)

The Mist Egg is won after beating the three troglodytes in the Durham Cave. It's impossible to miss this egg - you'll obtain it during the main quest. This egg is very helpful for buffing spells but also has very important magic such as Resurrect, Crackle, and Crackling.

(Fire/Earth/Explosion, Earthy Mana Egg)

The Gravity Egg is dropped by the Eye of Valmar once beaten. This egg is one of my personal favourites due to the fact that it has Alhealer but contains a lot of devastating offensive spells such as BA-BOOM!

(Wind/Water/Lightning, Sagacious Mana Egg)

The Soul Egg is obtained by beating the two Crimson Tails in Ceceile Reef. It contains useful Wind and Thunder magic as well as a couple of healing abilities. There's not much else to say about this one, however.

(Lightning/Explosion, Ultimate Mana Egg)

Obtained after the boss fight with the two Naga Queens in Demon's Law. It contains very useful Fire and Thunder magic as well as status effect magic such as Resurrect and Cure.

These eggs are optional and obtained only through optional content within the game.

(Recovery/Assistance, Defensive Mana Egg)

After reuniting with Roan in Cyrum Kingdom, venture back to Raul Hills to find a special stage. Head towards the ruins and make your way through the devils until you reach the Guard's tower. These devils are considered some of the hardest enemies in the game (excluding bosses) due to the fact that they are able to cast BA-BOOM! which can very easily K.O. your entire party at once. Try to avoid them as much as possible and if you find yourself in a fight make sure you cancel as much as possible. This egg contains all of the healing spells you'll need as well as a variety of helpful buffing & de-buffing spells.

(All Attack Magic, Offensive Mana Egg)

This egg is obtained in the Birthplace of the Gods after all 3 lights are lit. Return to the first level and extinguish the light of the Blue Earth. Enter the room of mirrors next to it and slide the two mirror blocks in to their shadows. Run to the end of the hall and use the light source to send a beam of light in to the Blue Earth. A chest will lower that contains the Mana Egg. This Mana Egg is interesting due to the fact that it purely contains offensive combat magic from all of the elements.

Thanks for reading! Feedback is welcome and definitely appreciated. Good luck in Grandia II!