Like in the previous installments, completing missions is necessary to advance through the storyline. For the most part, missions are available from the Via Senatus. Missions that you have taken on previously or are currently in the process of completing can be viewed from "Main" under "Book" and then "Missions".
Information for missions will show when it becomes available, the in-game description, summary (when you press 
on a mission), how to complete it, and the reward. For more information on completing missions, reference the guide and it's maps. As of right now, the list of missions is incomplete.
Prelude to the Forest[edit]
Available: At the start.
Description: Anyone daring to survive as an explorer here in Armoroad must first pass the Senatus's official test. You have been tasked with creating a map of B1F.
Summary: Fill in the specified area of B1 on your map!
How to Complete: Head to B1F and map out as much as possible then report the map to the guard.
Reward: Ariadne Thread is now sold at Napier's, and further access to the Labyrinth.
Proof of Will[edit]
Available: Shortly after reaching B4F.
Description: The Senatus wishes to gauge the strength of those plumbing the Labyrinth's depths. If you would answer their call, then defeat the beast Narmer on B4F!
Summary: Defeat Narmer on B4F!
How to Complete: Head to B4F - A6 and enter Narmer's room, defeat Narmer and report at the Senatus.
Reward: Access to the 2nd stratum and the Iron Naval Ram from the harbormaster.
Danger in the Undersea Grotto[edit]
Available:
Description: A mysterious woman calling herself Olympia has been seen frequently in the Undersea Grotto. Take her into custody and bring her to the Senatus!
Summary: Pursue Olympia, who vanished in the forest.
How to Complete: Head to B7F - D5, afterward head to B8 - A2, you will get thrown into combat with an Abyssal Death, after defeating the FOE, return to the camp in B7, report to Kujura, then report to the Senatus.
Reward: 2000en, 30000 exp.
Door to the Deep City[edit]
Available:
Description: Use the Sea Bead to locate the enigmatic Oceanmaster Ketos. Meet and speak with this being to learn more about the Deep City, and, if need be, defeat it!
Summary: Find the legendary Deep City at the bottom of the sea!
How to Complete: Head to B6F - B3 and use the Sea Beads, afterward head to B7 - D1 and go down the now accessible hallway and head down the stairs to B8. Follow the path until you find Ketos and defeat it.
Reward: 3000en, 45000 exp. You may now head to the Deep City and the 3rd Stratum.
Otherworldly Visitors[edit]
Available:
Description: The Deep City's raison d'etre is the war against the otherworldly Deep Ones. Enter the Hall of Conviction to learn about the threat these monsters pose.
Summary: Go to the Hall of Conviction located on the 3rd Stratum.
How to Complete: Head to B10F - C4 and talk to Olympia. When you enter the Hall of Conviction, you will get thrown into a fight with a Deep Lady and a Deep One, after defeating these two, return to the Celestial Palace in the Deep City and report the mission.
Reward: 5000en, 65000 exp. You may now also explore past B10F.
Branching Point[edit]
At this point, you can choose to back either city. Backing a city allows you access to their missions in addition to their respective hidden class. Further down the road, you will have one final choice as to who to go with. This is the point where the "True" path comes into play.
Slay the Gatekeeper
Available: Shortly after reaching B12F.
Description: Our agent Kujura has infiltrated the underground Labyrinth and reports of a gate leading to a deeper Stratum. Slay the guardian of that gate!
Summary: Slay the Gatekeeper!
How to Complete: Head to B12F - D4 and defeat the Gatekeeper, then report to the Senatus.
Reward: 7000en, 85000 exp, and General's Baton (Shogun class unlocked).
Search for Amarantos
Available:
Description: Legends whisper of the Amarantos flower, which never wilts or loses its color. It may be found in the Abyssal Shrine; I need that flower to help the Princess.
Summary: Find the Amarantos said to be in the depths of the Abyssal Shrine.
How to Complete:
Reward:
Locate the Teleporter
Available:
Description: It seems a teleportation device exists on the Fourth Stratum that connects to the Porcelain Forest. Find it before the denizens of the Deep City do!
Summary: Find the teleporter said to be in the depths of the Abyssal Shrine!
How to Complete:
Reward:
Hunt for the Abyssal King
Available:
Description: The Abyssal King and his attendant Olympia have invaded the Porcelain Forest and seek to end the Princess's life. Find them and stop them!
Summary: Find the Abyssal King who is threatening the Princess!
How to Complete:
Reward:
Protect the Gatekeeper
Available:
Description:
Summary:
How to Complete:
Reward: 7000en, 85000 exp, and ??? (Yggdroid class unlocked).
Available:
Description:
Summary:
How to Complete:
Reward: