The War of the Fae Courts

The War of the Fae Courts raged through the realm of Fae Home through pretty much the entirety of the the First Age.  There were long stretches of time without fighting, but peace was never declared
The vast majority of Fair Folk were heavily influenced in their appearance, powers, and mannerisms by one of the four elements of fire, water, air, or earth.
About one fae in fifty had relatively minor elemental aspects, these fae were sometimes treated as second class citizens. Only about two Fair Folk in a hundred lacked an elemental aspect entirely.  These court-less fae were alost universally reviled as pariahs and outcasts by the majority of elemental fae.
The vast majority of Fair Folk at this time pledged their political allegiance to the nobles of one of the four courts.  Fire aspect fae pledged loyalty to the Fire Court, water aspect fae pledged loyalty to the water Court, earth aspect fae pledged loyalty to the Earth Court, and air aspect fae pledged loyalty to the Air Court.
A few mavericks and nonconformists rejected their courts and declared themselves neutral or court-less but no one defected from their "native" court in order to join a rival court.
The leaders of every court wanted to be the dominant elemental power in the realm of Fae Home.
The war was not fought in a conventional manner.  If a group of water fae occupy an empty region of Fae Home, the area in question will gradually get wetter and wetter while the local flora and fauna adopt more watery traits.  If a group of fire fae occupy an empty region of Fae Home, the area in question will gradually get hotter and hotter while the local flora and fauna adopt more fiery traits, and so on and so forth.  The main objective of the War of the Fae Courts is for each side to occupy as much territory as possible and terraform their holdings into their preferred environment.  The various courts would use force to kill or push out members of rival courts in their claimed territories.
Complicating this is issue is that all four sides controlled small fortified realms that were so keyed to one of the four classic elements that the natives cannot be dislodged even if the other three courts allied against them.  
The four courts made and broke temporarily alliances frequently.  If one of the four sides seemed to be growing dominant, the other three would form a temporary truce to drive back to their home holdings only for their truce to break down almost immediately allowing the ganged up on power to rebound.  Over thousands of years, no side could gain a clear and lasting advantage, gaining nothing but a growing list of vendettas and grudges against the other three courts.
During the First Age, most mortals, be they mighty dragons or lowly kobold, had no idea that the Fair Folk were locked in an eternal war.  Few Fair Folk were willing and able to enter the mortal plane, and most of those fae that mortals encountered were mostly those who were deserters of non-participants from the War of the Fae Courts.
The First Unmaking destabilized the realm of Fae Home as much as it did the mortal plane.  A lot of fae were irreparably changed, many became remnants others changed less dramatically but the effects were noticeable none the less.
Some of the seemingly unchangeable elemental strongholds altered and other "neutral" areas picked up new elemental influences seemingly at random.  New terrifying varieties of sprites emerged.  Successive generations of Fair Folk were altered even more.  The number of court-less fae and fae with weak elemental aspects exploded.
Fair Folk  can draw on the energy of the Elemental Plane for their sustenance, magical power, and building materials.  Once this was easy and reliable process but after the First Unmaking, this process became much more difficult and dangerous forcing more and more fae to enter the moral plane to make up for their shortfalls.
As day-to-day survival became more of a an issue, mass numbers of Fair Folk began to question why they should obey their court leaders and fight a questionable war while the entire home plane was seemingly disintegrating.  Mass desertions occurred in all four elemental courts and those that remained and kept following orders now followed their orders with less enthusiasm often obeying the letter of their rulers' edicts in a matter that contradicts the spirit of their laws.
While peace was never declared, the War of the Fae Courts wound down gradually over the centuries of the the Second Age.
While the Second Unmaking did not impact Fae Home as severely as the First Unmaking did, the leaders of the four courts did agree to an armistice putting the War of the Fae Courts on pause.

The Conflict

Outcome

The four warring courts signed a temporary truce/armistice in order to handle the threat posed by the Second Unmaking and this armistice was never concluded even after the immediate threat from the Void was seemingly contained.

Aftermath

One lasting repercussion of the millenia long war with no clear resolution is that this undermined the faith most Fair Folk had in their court leaders.  Now most fae only pay their traditional rulers mere lip service while others are in open defiance of them.

Historical Significance

Legacy

Even now, well into the Third Age the armistice remains in place and the courts are in state of uneasy peace. There are some hardline traditionalists that want to resume the old war and there are some radical reformers who want to create a lasting peace treaty establishing formal cooperation between the courts. Most Fair Folk are content with the armistice as is because individual fae have more freedom and autonomy now than they had at any point in the past.  These modern modernists oppose both fringe factions seeking to alter the new status quo.

Conflict Type

War

Battlefield Type

Extraplanar

Conflict Result

A bitter stalemate and uneasy peace.

Location

Fae Home