Aesir-Vanir War

The Aesir-Vanir War, also called The First Great War or The Long War, was a war fought between the @Aesir and @Vanir Gods many years ago. It led to the unification of the two tribes as a single pantheon.

Prelude

After years of simmering hostilities between the Aesir and Vanir Gods over the murder of Ymir, the Vanir God @Freyr attempted to improve the relationship between the two factions. Traveling to Asgard, Freyr taught the Aesir how to use techniques in Vanir magic in improving crop yields and producing bountiful harvests, which would be enough to feed all of @Asgard. However, because the Aesir were too impatient and not well disciplined in Vanir spellcraft, their attempts at using magic ended up going wrong. As a result, Freyr was wrongly blamed for it and was accused of sabotage. A mob of minor Aesir gods then proceeded to tie Freyr up before burning him alive.

However, he managed to survive and took the opportunity to escape back to @Vanaheim. Enraged by what happened, the Vanir swore revenge against Asgard. Due to his traumatic experience at being burned alive, Freyr wasn't the same after that, but only for a while. His carefreeness was replaced with fear, paranoia, and fits of rage. Even after he's back to being his old self, he never forgot the time he was burned alive and his hatred for the Aesir and @Odin Borson remained intact.

Assault on Vanaheim

After a series of skirmishes between the two sides, @Odin Borson, the head of the Aesir, assembled a large army and marched towards Vanaheim. Though the Aesir initially dominated the battle through brute force and Odin's leadership, they were eventually repelled by the Vanir's magic.

During one battle, the Aesir demigods Magni and Modi encountered the Vanir goddess Nerthus. Through teamwork, they were able to defeat and kill her.

Aftermath

Eventually a truce was made. As an agreement, the gods all spit in a barrel and created Kvasir, the god of wisdom. Also, each of the tribes send a member to the other in the peace treaty: Frey, @Freya and Njord went to Asgard while @Mimir and Honir went to Vanaheim.

However, Odin eventually grew paranoid of the @Jotunn and their prophetic knowledge of Ragnarök. After Odin was banished from Jötunheim for trying to steal their knowledge, Odin ordered Thor to use @Mjølnir to slaughter all the Giants across the realms, which caused Freya to begin loathing the Aesir.

After the marriage between Odin and Freya ended, the Aesir re-invaded Vanaheim. Without Freya's leadership, the Vanir were overwhelmed by their numbers and tactics, and most settlements in the realm were obliterated, their ruins then occupied by Einherjar. In particular, the crater in the northern region of Vanaheim had its river blocked, leading to a drought, and most of the Vanir living there were killed during a battle between Laufey and Thor. The surviving Vanir and their supporters either retreated to the jungle to continue the fight under their new leader Freyr, or, in the case of non-combatants, concealed themselves with magic.