This page explains how to complete the level 80 post-Shadowbringers quest "Vows of Virtue, Deeds of Cruelty".
This quest is available if you have completed the quest Moving Forward.
Starting the Quest
Talk to Alphinaud in Eulmore to begin the quest.
Speak with the Crystal Exarch
Teleport to the Crystarium and use the Aetheryte to go to the Dossal Gate, then go east up the stairs and talk to the Crystarium Gatekeep and say Yes to enter the Ocular. Talk to the Crystal Exarch to proceed. There will be a cutscene.
Speak with Tataru
You can either teleport to Mor Dhona, or you can use the Portal to the Source in the Ocular and say Yes to travel to the Source, then go southwest and check on the Exit to North Silvertear and say Yes to go to north Silvertear. Enter the Rising Stones and talk to Tataru to proceed. There will be several cutscenes. Say Yes if you are ready.
Solo Duty: Vows of Virtue, Deeds of Cruelty
Your hotbar/crossbar is replaced with a small number of actions. Use Coerthan Torment Combo to do a multi-target attack on the enemy. Use Skydragon Dive to rush to the target and do a multi-target attack. Use Aqua Vitae to restore some HP. Sort Pet Hotbar allows you to change the order of these actions.
Defeat the enemies that attack you. In the first wave, defeat the Signifer and Medicus in the back first. After the first wave, there are two Praedator Praetoriani that will sometimes use line attacks and circle attacks. Later, you will battle a Scorpio Praetorianus and Colossus Praetorianus. The Colossus will use line attacks and cone attacks. You can keep the Colossus turned away from Gaius to reduce damage to him. You will also have to dodge line attacks from Annia and Julia quo Soranus, who are untargetable.
Afterward, follow Gaius. After you are on the lower level, go north through the doorway, then turn right to go into a side hallway. Keep following the path and there will be a cutscene.
Your hotbar/crossbar is replaced with a small number of actions. Ala Morn is a single-target attack that restores some of your HP. Drachenlance is a single-target attack that inflicts damage-over-time status to the enemy. Horrid Roar is a multi-target attack. Use Stardiver to rush to the target and do a multi-target attack. Dragonshadow Dive is a Limit Break. It will only be available at a specific time in battle. Sort Pet Hotbar allows you to change the order of these actions.
Use Drachenlance to inflict damage over time, and use it on Arch Ultima again whenever it is available again.
Arch Ultima will perform line attacks.
Eventually, Signifer Praetoriani will load data into Arch Ultima, and it will start using Angry Salamander, a line attack, and the Signifers will repeatedly use Fire II, a circle attack. After the Signifers become targetable, use Horrid Roar to defeat them. Arch Ultima will then cast Terminus Est, and will have arrow indicators in front of it. Make sure not to stand in the path of any of these arrow indicators.
Two Lembus Praetorianus will appear. Use Horrid Roar to defeat them.
Eventually, Signifers will load more data into Arch Ultima. After the Signifers become targetable, use Horrid Roar to defeat them. Arch Ultima Bits will appear. Arch Ultima will cast Arch Cutter, multiple cone attacks originating from the boss, and the Bits will cast line attacks that cover the safe areas between the cones. Use Horrid Roar to defeat the bits.
Later, Signifers will load more data. After the Signifers become targetable, use Horrid Roar to defeat them. Arch Ultima will become invulnerable. After some dialogue, Dragonshadow Dive (the hotbar/crossbar Limit Break) will become available. Use it. There will be a cutscene.
Speak with Tataru Again
Talk to Tataru to complete the quest. There will be a cutscene.
Next Main Scenario Quest
After you complete the quest, talk to Krile to accept the next quest: Old Enemies, New Threats. There will be a cutscene.