You're wandering around the Presidium Commons in Mass Effect 3, probably just trying to stock up on fish or check your email, when you overhear a Volus who sounds like he’s having a total meltdown. He’s not talking about the Reapers—at least not directly. He’s obsessed with a religious text. This is the start of the Irune: Book of Plenix quest, and honestly, it’s one of those missions that makes the galaxy feel a lot smaller and more desperate.
The Volus in question is standing near the Elkoss Combine Arsenal Supplies kiosk. He’s venting to a Salarian about how his people have lost their way. According to him, the Book of Plenix is this ancient scripture that basically mandates charity and the forgiveness of debts during times of war. Since the Reapers are currently chewing through the Volus homeworld, Irune, he thinks the book is the only thing that can remind his species to be decent to one another.
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Why you can't find Irune right away
Here is the thing that trips everyone up. You get this quest pretty early—usually right after Priority: Palaven. You open your galaxy map, look for the planet Irune, and... nothing. It’s nowhere to be found.
You haven't glitched the game.
The planet Irune is located in the Aethon Cluster, but that specific cluster doesn't even show up on your map until you finish Priority: Tuchanka. If you’re currently helping Mordin with the genophage cure, just keep pushing through the main story. You can't force the cluster to appear any sooner.
Once you’ve cleared Tuchanka, the Aethon Cluster pops up. You’ll want to head to the Aru system. Irune is the first planet you’ll see, tucked right near the sun.
How to actually get the book
Don't expect a big ground mission here. You aren't landing the Normandy or getting into a firefight with Cannibals. This is a "Search and Rescue" style mission, which is basically code for "ping the planet and scan it."
- Go to the Aru system in the Aethon Cluster.
- Find the planet Irune.
- Scan it to find the "Book of Plenix" artifact.
- Watch out for Reaper alertness—if you ping too much, you'll have to high-tail it out of there.
If for some reason you missed the conversation on the Citadel earlier, you can actually stumble upon the book just by scanning the planet anyway. The mission will still pop up in your journal as Citadel: Book of Plenix.
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Turning it in (and the rewards)
After you’ve got the book, head back to the Presidium Commons. The "Angry Accountant" (as the game files sometimes call him) is still there by the bank. Hand it over, and you’ll get a nice little bump in your Citadel Defense Force War Assets. Specifically, it adds 7 points to your total Military Strength.
It’s not a game-changing amount of power, but in Mass Effect 3, every point counts toward that "best" ending. Plus, you get some experience points and 15,000 credits, which is a decent chunk of change if you're trying to buy those expensive Spectre weapons.
The missable window
There’s a bit of a weird timing issue with this quest. If you go and get the book before the Cerberus attack on the Citadel (Priority: The Citadel II), you might find that you can't turn it in immediately because the Volus disappears during the chaos.
Don't panic.
He comes back once the station is secure. Just make sure you finish the hand-off before you head to the Cerberus Headquarters at the very end of the game (Priority: Cerberus Headquarters). Once you start that final stretch, all these little "fetch" quests are gone for good.
Is it actually worth doing?
Kinda. From a lore perspective, it’s cool. It shows that while the Turians are fighting with guns and the Asari are using biotics, the Volus are fighting a different kind of battle—a battle for their own culture. The Book of Plenix represents their version of the "greater good."
If you're playing the Legendary Edition, the requirements for Total Military Strength are a bit more forgiving than the original 2012 release, but skipping too many of these scanning missions can still leave you short of the breath-scene ending.
Basically, it takes two minutes. If you’re already in the Aethon Cluster looking for fuel or other artifacts like the Volus Fabrication Units, you might as well grab the book.
Next Steps for Players:
Check your galaxy map for the Aethon Cluster. If it’s not there, go finish the Tuchanka missions first. Once the cluster is open, fly to the Aru system and scan the innermost planet to wrap this up quickly.