Dissension in the Ranks
Locations: Elaaden, Eos
Check your email after completing Hunting the Archon for a message about battling kett ships that have crashed on Elaaden.
Follow your nav to some black smoke, and some battling kett. While in theory you're here to investigate possible kett allies, these aren't them- so mow 'em down..
It's just Chosen and Wraiths- when they're all down, scan the wreckage for a data pad that's not immediately hackable
Talk to Suvi aboard the Tempest. If you have the kett samples from Know Your Enemy, she'll direct you to Lexi in the med lab (otherwise, you'll want to complete that quest now). With Lexi's data, Suvi unlocks the pad, pointing you to a broadcast point on Eos.
The map for the broadcast point can be a little confusing, but the the location you're looking for is actually in a cave-tunnel beneath the plateau here, running northwest/southeast (just follow the roads). Clear the kett from the cave, then look around. If you haven't been here before, there is a wayward escape pod to scan, and a container right next to it.
On the other end of the cave are two containers, an audiolog from a tortured Salarian (presumably the escape pod occupant), and the broadcast device you're looking for.
Scan it to confirm it's just a redirected signal, and follow your nav to the next relay station. This one is shielded, with kett trying to break through.
Kill the kett, disable the generator, then scan the node to get the location of the next relay.
Relay three is in the Presson Dunes. This one is under attack by kett and challyrions, but kill them all (as per usual), disable the generator, and scan the relay.
This leads to a final building, guarded by a large number of both Chosen and Anointed.
Be careful about rushing ahead- there are so many automatic weapons here that you can lose shields almost instantly. Use the light cover to snipe or at least scatter the enemy a bit before moving in for the kill. When the ground is clear, enter the building and activate the console for an interesting chat.
The Primus offers an alliance of sorts against the Archon. You can accept, for a bonus in the final fight, or decline on principle. There's also a bug where the conversation ends without you being able to make the choice at all, but this seems to default to the 'refused alliance' choice.
Before you leave, you can loot the large container here, scan a core, and listen to several informative audiologs.