Overview
The Thalassai invasion is the external invasion of Thalassai by the Alliance against Thalassai, whose campaign brings together Virel, Nahm, Morozkaya, Haverloch, Brighthaven, Ozaith, and forces from Ulzathir. The invasion begins after Thalena captures Pyrathalor and keeps his essence; Morozkaya, Haverloch, Brighthaven, and Ozaith then commit to the war against Thalassai.
The Thalassai Invasion fails. Thalassai survives, and the surviving attackers retreat.
Background
Ozaith keeps an ocean barrier between Thalassai and Valrindor because he fears Thalassai's rise and Thalena's power. Virel infiltrates Thalassai with Nahm's guidance, enters the Thalassai legions, and studies Pyrenis, Chronasis, the imperators, and Thalassai's government. Haverloch uses his intelligence to plan a strike before Thalassai can cross the ocean.
The alliance commits to the invasion after Thalena publicly rejects divine rule and names Cassian as a godslayer capable of killing gods. Pyrathalor descends against her near Chronasis. Thalena traps him in a black hole spell and captures his essence. With Morozkaya's god gone, Kazimir, Kyrana, Vianna, Virel, Nahm, and their allies commit to the attack on Thalassai.
The coalition forms through overlapping motives. Morozkaya wants Pyrathalor restored, Haverloch follows Virel and Nahm's calculations, Brighthaven supplies ships and Isaac's healing, and Ozaith contributes Ulzathir forces through Ozaryn and his fleet. Jin travels with the force to protect Thalia and speak to Thalassai first. Lythariel comes to protect Cassian.
Campaign
After the fleets pass Ozaith's ocean wall, Virel splits the Thalassai Invasion between Terranova, Pyrenis, and Chronasis. Ozaith's forces move toward Terranova, Brighthaven and Haverloch ships attack Pyrenis, and an elite strike force of about one hundred level-eight-or-higher mages crosses the southern darkness toward Chronasis.
Thalena prepares Chronasis for the strike against the capital. She clears civilians from the roads and villages around the capital, positions defenders and shields, gives Pyrathalor's essence core to Aelius, and sends Aelius, Silas, and Arinella through the void to ambush the attackers moving on Chronasis. She also assigns Lunorax to meet Nahm if the god descends and holds Cassian back until Ozaith enters the battle.
The Chronasis strike collapses quickly. Aelius, empowered by Pyrathalor's core and fighting alongside Silas and Arinella, devastates the attacking force and defeats Ozaryn. Silas and Arinella move through the void to heal Thalassai defenders, kill isolated attackers, and keep Aelius, Tazarin, and other Thalassai fighters active at Chronasis. Virel fights Tazarin. Isaac keeps the attackers alive long enough to continue.
Nahm descends when the Chronasis strike turns against the attackers. Lunorax answers by overloading his stored essence, combining temporal and air magic fast enough to evade Nahm's vectors, cut apart a massive meteor, and damage Nahm's descended form. Lunorax then cracks apart and vanishes, buying Thalassai the time Thalena expected him to buy.
Thalena then fights Vianna, Kazimir, and Kyrana. Their fire, ice, lava, and plasma disrupt her casting for a time. Thalena eventually traps them with the same black hole-and-shield method she used against Pyrathalor. Kazimir and Kyrana are pulled into the vortex and killed. Isaac breaks the shield and detonates the black hole before Vianna dies, leaving only a small remnant of the strike force.
Tianlei then descends and strikes Thalena, fulfilling a private deal she had made with him. Ozaith descends afterward, demands that Thalassai submit to him, and summons an asteroid large enough to threaten Xolterra. Aelius brings Pyrathalor's core to Cassian, Silas carries Cassian to the battlefield, and Hrzai stabs Ozaith with a golden sword. Cassian uses Pyrathalor's power and his godslayer ability to crush Ozaith's essence.
Thalena takes the remaining Pyrathalor core from Cassian, drains it completely, and uses a black hole to consume Ozaith's asteroid before it can strike. The blast breaks her body further, and Cassian and Jin catch her as she falls back toward Chronasis. Thalena then vanishes in Cassian's arms. Thalassai survives and loses its leader.
Aftermath
Thalassai responds by choosing Cassian as the new archon of time. The archons, imperators, legati, chronarcs, and regional leaders rally around him, and Tazarin is welcomed as archon of cosmos when Thalcoris enters Thalassai's government. Pyrenis suffers damage and legion deaths. Most civilians are spared. Terranova remains largely intact after the siege of Terranova, with food production at full capacity. Cassian orders rebuilding in Pyrenis, Terranova, Thalmyris, and the villages around Chronasis, expands ocean patrols, and begins preparing Thalassai for surviving enemies.
Morozkayan survivors return to Kyranthos after losing Pyrathalor, Kazimir, and Kyrana. Vianna leads alongside Ivan, Liana, Virel, Maia, and the Morozkayan council. The country survives. The council restores Kyranthos's rivers, lava channels, and city services while Morozkayans mourn the god they worshiped as bound to the land.
Ozaith's open rule over Ulzathir ends after his death. Zain returns from the failed Thalassai campaign, conceals Ozaith's death from the public, takes control in Ishtanur, and uses Ozaith's hidden death to militarize Ulzathir and launch the Ulzathir Invasion of Solvarria.
The surviving coalition gains no clean victory. Hrzai's intervention leaves Ozaith and Pyrathalor dead, Xalmyrra freed from its cycles, and both Thalassai and Valrindor badly damaged.