The Twin Gods' Wrath

Credits to Sie Nguyen from Artstation for the awesome cover art!

In the early years of the War Against Orakgra, the Camaerithian Concordwas desperate for a way to break the stalemate of the Years of Strife. And so, the Ilthinaluvars (Archmages) of the Camaerithian Circle and the Arcanul Ordinate devised a spell that could both wipe Orakgra from the map and restore the peninsula of the Arakhor Tathra they had deforested. This spell was dubbed The Twin Gods' Wrath by some of the more zealous mages who worked on it, and was meant to be a spell of such power to rival the titanic rituals of the Age of Rebirth.
Thankfully for Orakgra and the future of war in Emaxus, the spell failed. Had it worked, Orakgra would have been utterly annihilated and the Camaerithian Concord would have ensured their unequivocal military and magical supremacy over any other faction on Emaxus.

The Spell's Purpose

The Twin Gods' Wrath was meant to be a ritual that could link together the arcane abilities of powerful mages and then channel their power through the knowledge and experience of an archdruid(s). This unity of power and purpose, in tandem with the ritual site and components needed (and listed in "The Spell Itself" below) would allow the casters to create another Wild Heart and cleanse Orakgra from the southeastern peninsula of the Arakhor Tathra -- "coming back stronger," in the words of some of the spell's creators. By the final theoretical construction of the spell, the believed fallout would be a new Wild Heart over the current position of the city of Orakgra itself and the instantaneous creation of dense forest across the deforested peninsula. In order to fuel the instantaneous creation of millions of megatons of organic matter, every single molecule of Orakgran impact on the ecosystem would be repurposed: every person, every building, every tool and weapon, would instantaneously be converted into raw biomass and then transformed into the Arakhor Tathra.
If the Twin Gods' Wrath had worked, it would've meant the reinvention of total war on an unimaginable scale. Salting fields and burning cities is one thing, but converting every miniscule memory of an entire civilization into forest by way of an arcane superweapon is something else entirely. Thankfully for all Emaxians, the Twin Gods' Wrath did not work. 

The Spell's Outcome

There were eighteen people present at the ritual site of the Twin Gods' Wrath: twelve arcanists (including the three Ilthinaluvars of the Camaerithian Circle), three archdruids from the Circle of the Heart, and then three military observers from the Concord. Seven survived. Ilthinaluvar Aninyel Elendiir, Archdruid Iliphar Finlee, two military observers, and four other arcanists died in the arcane disruption that formed when the ritual casting of the spell was completed. Those who survived have refused to discuss what happened at the ritual site.
Immediately following the failure of the Twin Gods' Wrath, the arcanists who survived unilaterally agreed to sink the clifftop, shoreside ritual site to the bottom of the frothing Silver Sea below. The surviving military observer, who remains unnamed, was in a coma for a month, and the surviving archdruids focused on trying to heal the surrounding land of the arcane fallout. To this day, no one but the eight survivors know where the spell's casting was attempted. Twelve years later and the War Against Orakgra still raged. Then, the Chosen arrived.

The Spell Itself

The Twin Gods' Wrath

10th-level transmutation
Casters: 15
Casting Time: 3 days
Range: The same plane of existence as the casters
Components: V, S, M (every spell slot from every day from every caster, which must contain at least 12 9th-level slots by the end of the casting; a seed of the Wild Heart infused with the soul of an ancient nature spirit; arcane ink worth at least 500,000 gp)
Duration: Permanent
For the duration of the casting of this spell, all 15 casters must remain linked by hands around an arcane circle inscribed with runes using the arcane ink required for the casting of the spell. During the final day of the casting, every caster must open their consciousness completely and become of one mind and purpose.
When the casting is complete, every caster imagines the point where the spell will be cast. Every creature, object, and structure within 300 miles of that point takes 200 force damage and 200 radiant damage. If this damage reduces them to 0 hp, they are killed outright and immediately converted into the forest this spell creates. Creatures killed in this way can only be returned to life by way of a Wish spell.
Immediately after the casting of the spell, a new tree at the scale of the Wild Heart (a mile or more tall with a several mile wide canopy) and all land within the radius of the damage of the spell is converted into dense, magical forests. The souls of those killed are converted into nature spirits, who populate this new forest in the form of awakened plants, ents, or other natural and magical creatures.

A Monolithic Undertaking

The development of the Twin Gods' Wrath had technically been underway for centuries. In the earliest days of the Age of Extant, the handful of Camaerithian mages and druids who survived the Reckoning knew of the great magical mysteries that had been lost in the God-Wars. Among these were spells and rituals far beyond the limits of the knowledge they had -- and any knowledge that has been regained since then. These monumental spells could've been the key to Camaerithian survival and even regrowth after the devastation of the Reckoning. At least, that was a theory a handful of these arcanists had; however, as decades became centuries, these theories were buried and attempts to reclaim or restudy the arcane knowledge necessary were abandoned.
Until the arrival of Orakgra and the Years of Strife. When it became clear that any quick end to the war would come at an unjustifiable cost in lives and the Arakhor Tathra, and that the stalemate would likely continue for far longer than was palatable to the Concord, the Protectorate and the Camaerithian Circle started a top-secret project to devise a ritual that would simultaneously eradicate Orakgra and restore the nature they had devastated. This project was dubbed "Operation: Holy Wrath" and put in the hands of the Ilthinaluvars of Camaerith and the most powerful and most loyal Theussaun battlemages. Some, like Aramoira, felt that the project was not only wrong but also a repetition of the mistakes of the Age of Rebirth that led to the Reckoning. Others believed it was a pipe dream and a waste of the Concord's time and efforts.
Both, in one way or another, would be proved right. Collection of the necessary components and testing different components countless times to find a working theoretical construction of the spell cost an unimaginable amount of money and time for the Concord. Totals are uncertain, but total cost in coinage is estimated to have tallied in around ten million gold pieces over the six years that Operation: Holy Wrath was functional. And all that came of the project was a handful of dead archmages and archdruids, a handful more disgruntled and disillusioned arcanists, and a demolished cliffside.