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"Underground Investigation" is a mission in Armored Core: Last Raven and Armored Core: Last Raven Portable. It is the last mission in Pulverizer Path 1 and continues the story arc of the Unknowns being unleashed on the world again. The player enters the Internecine, survives the Unknowns and destroys Super Bipedal Pulverizer.

The YH08-MANTIS is the reward for S-rank completion.


Requester: Alliance Tactical Unit

Operation Area: Underneath Circ-City

Objective: Investigate the area beneath Circ-City

Reward: 180,000c

Start Time: 05:03

Mission Summary[]

This mission request involves investigating the area beneath Circ-City.

There must be something there that will explain Vertex's intention to launch an attack.

Ed Weisz


Although we faced fierce resistance from Vertex, our forces managed to secure an entry route leading into the area beneath Circ-City.

Based on the desperation with which Vertex fought, we have reason to believe that something relating to the ongoing conflict is concealed there.

Our forces suffered heavy losses during the last battle and we don't have the manpower to conduct a survey of the underground area. We'd like you to do so instead.

It's unknown what type of dangers exist in the area, but Jack's declared time of attack is at hand and we're running out of options.

This will most likely be the final battle, Raven. Good luck.



Mission Intro[]

Sheila:We're almost at the operation area.

Sheila:This is probably your last battle. Promise me you'll come back alive...

After Mission Begins

Sheila:Raven, my scanner is picking up a lot of activity!

Sheila:Do what you can to avoid being hit.

Sheila:They just keep coming...

Sheila:There's no end to them...

Sheila:Hang in there, Raven.

Sheila:What can I do...?

Sheila:It can't end like this...

When Jack-0 Releases The Gate[]

Jack-O:Raven, over here!

Sheila:The gate is unlocked. Get out of there!

After Arriving Inside the Opened Room[]

Jack-O:You made it...

Sheila:What happened to Jack?

Jack-O:Look at me... This is what happens when you step over the line...

Jack-O:It was foolish to think we could control it...

Jack-O:You're the only hope now, Raven.

Jack-O:You must not fail...

After Falling Down Into The Shaft[]

Sheila:It's time. This is it...

Sheila:I don't know what lies ahead, Raven.

Sheila:Please be careful.

Sheila:This must be what Jack was talking about.

Beginning Of The Battle[]

Sheila:Something's wrong here, Raven.

Sheila:Keep your distance and stay alert!



Sheila:I thought so... Someone's onboard that thing.

???:You'll regret this...

???:You're one as well...

???:A Dominant...

Sheila:You did it...

Sheila:I'm glad you're okay. Let's head out.


The following information is "gray area" content — it may not be completely factual, and/or falls under YMMV territory.

As soon as the mission begins, Unknowns will bombard the area, most of them them going directly after the player's AC. These cause stun and pretty high heat upon impact, which means that certainly more will hit. The only way to survive is to keep moving non-stop, that means no Boosting as insane as that sounds, just keep holding down the move button. There is a bit of a glitch or at least an exploit where by running into the central tower, the majority of the Unknowns will hit the tower, saving the player's AP for the real fight.

After a while, the Operator will talk about the number of Unknowns and eventually Jack-O will open a door on the far side. If the player choose to boost around to dodge the Unknowns, it may take some time to find the door. Upon entering, you will see a cutscene where Jack-O is heavily damaged and dies shortly there after. There is an blasted open section of the wall leading to a shaft. By going down where, the player starts the second half of the mission.

Here the Super Biped Pulverizer is found and the pilot of it is Evangel. This Pulverizer operates in a similar manner as its normal brethern but has a unique wave beam that it frequently uses and, if it hits, it will cause massive damage. It must stop to perform this attack and launch its laser blasts and this is really the only time to attack it, otherwise it is too mobile and most attacks will miss. Once it is defeated, Evangel declares you a Dominant as the unit collapses, finishing this path.


Missions in Armored Core: Last Raven
Time - 08:00 "Destroy Military Base" • "Eliminate Intruders • "Distribution Center Recon"
Time - 10:00 "Escort Allied MT" • "Acquire the Commodity" • "Destroy AC Sundial" • "Remove Bridge Defenders"
Time - 12:00 "Eliminate the Enemy AC" • "Recapture Storage Site" • "Pursue Withdrawing MT"
Time - 14:00 "Protect The Cargo" • "Retake Distribution Center" • "Recover The Cargo" • "Battle Challenge" • "Remove Lab Intruders" • "Investigate Enemy Activity" • "Investigate Research Lab"
Time - 16:00 "Destroy AC Vigilance" • "Destroy Raging Torrent IV" • "Destroy Enemy Squadron" • "Eliminate Enemy Invaders" • "Protect Allied Squadron" • "Destroy The Control Towers" • "Protect Transport Team" • "Destroy Transport Convoy"
Time - 18:00 "Halt Energy Production" • "Defend Against Assault" • "Secure The Terminal Area" • "Protect the ECM Devices" • "Rescue Allied Force" • "Seize The Airstrip" • "Destroy Suspicious Force" • "Eliminate Enemy Patrols" • "Destroy the ECM Devices" • "Destroy Power Generators" • "Prevent Plant Destruction" • "Destroy Underground Force" • "Eliminate Enemy Occupiers"
Time - 20:00 "Protect Reactor Core" • "Prevent Reactor Meltdown" • "Destroy Plant's Defenses" • "Shutdown Energy Plant"
Time - 22:00 "Eliminate Targeted Raven" • "Protect The Bridge" • "Track Down Evangel" • "Protect Warlord's Forces" • "Eliminate Zinaida" • "Destroy Air Assault Force" • "Destroy The Bridge"
Time - 00:00 "Eliminate Sorcerer" • "Protect Transport Train" • "Defeat Evangel" • "Help Allied MT Escape" • "Destroy Transport Train" • "Attack Distribution Center" • "Eliminate Plant Intruders"
Time - 02:00 "Investigate Recent Attack" • "Destroy Research Facility" • "Retrieve Research Data" • "Launch Preemptive Strike" • "Intercept Enemy AC" • "Defeat The Invading Force" • "Attack The Advancing Force"
Time - 04:00 "Shutdown Defense Systems" • "Destroy AC Sight Hawk" • "Destroy AC Heaven's Ray" • "Eliminate Airborne Force" • "Safeguard Industrial Area" • "Defeat Jack-O" • "Underground Investigation" • "Shutdown Internecine" • "Destroy The Internecine" • "Eliminate AC Intruder" • "Stop Last Assault Attempt" • "Destroy The Pulverizer"