Where's Irune and the book of Plenix?
I need to get the Book of Plenix from Irune, but I'm not even sure if that's a person in the Citadel or a planet in the galaxy.
Where do I find Irune?
Irune is a planet in the Aethon Cluster.
This system doesn't appear until you've advanced to a certain point in the main story (I believe after Tuchanka). Once you're able to travel there, you want to head to the Aru system (default from the relay). There you will be able to scan Irune to recover the book after pinging the planet.