Scan for Leviathan
Jump to Sigurd’s Cradle and head to the Psi Tophet system. Find the planet 2181 Despoina and scan near it. Scan the planet itself to find Leviathan.
Note: This next mission can be very tricky so make sure to bring along biotic teammates and equip your most powerful weapons/mods. Cryo is a lifesaver so have someone who can freeze enemies or use cryo ammo.
Arriving on Despoina
The first thing to note is to keep an eye on the sky. One of your crew will mention this after a while so for now you can go treasure hunting. Go forward and slightly right and you will find an Assault Rifle Omni-Blade III and the M-55 Argus assault rifle.
From here, head right and pick up the survey data for 2250 Credits . More survey data lies slightly to the left and forward. This is also worth 2250 Credits . Further on lies some pure Eezo samples for another 2250 Credits. Near the building to the left are Star Charts worth 2250 Credits.
Continue on for more pure Eezo worth 2250 Credits (notice a pattern?) To the right, by the sea, is a Pistol Cranial Trauma III mod. If the Reapers have arrived already, don’t panic. Their appearance seems to coincide with the examination of various remains and datapads lying around.
Despoina Reaper Battle
As the Reapers arrive you must take cover at the back near the shuttle. A good vantage point is somewhere in the middle so you can see enemies coming from both sides and to the front.
Marauders, Cannibals and Husks will all be there to welcome you. Keep particular eye on the Husks who can appear out of nowhere to grab you so watch your flanks. Carefully pick off the various Reapers who set upon you, paying particular attention to the Marauders.
Keep fighting and if you get swarmed, move from cover to cover. Brutes will eventually make their appearance. If they get too close, keep some cover between you and pick them off. Make good use of any grenades in your arsenal to bring them down quickly.
After a while, Cortez will get the shuttle fixed and give some rudimentary cover fire. Once the last enemy is down, a pulse will send him hurtling to the ground. Your task is to go and save him from the Reapers who are bearing down on his position.
Before you go rushing off, deal with the new enemies. Check your flanks for any sneaky ones and move steadily towards Cortez. Some grunts will be stood up on a beam overlooking the crash site so be sure to shoot those down too.
Jump over the gap and take cover as the area is swarmed by troops. Pick them off at your leisure as there is no time limit; Cortez will be fine! Once Shepard signals the all clear go back to where the gap is for the salvage worth 1500 Credits . The beam overlooking the ocean has the Pistol Ultralight Materials III. You can now talk to Cortez.
Despoina Power Cell Battle
This is the tricky part. The best option is to run like hell between Cortez and the power sockets. The one on the left is much better guarded as there aren’t so many directions of attack there. Another option is to lure some enemies to one, pick up another cell and lure them to the other and so on.
Only kill any enemies directly blocking your path. If a Brute is where you need to go, lure it away and come back. You do not need to worry about killing the enemies as you’ll get a new toy to play with once the power reaches 100%.
If you get desperate, use the Hydra Missile Launcher where Cortez is, on beasties blocking your path, preferably Brutes. Be warned though as more will spawn once you’ve taken them down. Your squad make useful cannon fodder so spam Medi-Gel if they keep dying.
Once the power reaches 100%, run up the ramp to the giant mech but before climbing in, quickly grab the salvage of 2250 Credits . Now it’s payback time. Don’t worry if your team fall as you can single-handedly take on all remaining Reapers yourself.
Unleash hell with the missiles on Brutes and continually use the cannon to one-shot the grunts. You can’t die in the Mech and don’t get staggered if a Brute runs into you so let loose. Once it’s all over, walk the Mech to Cortez. Well done! The hard part is over.
Breaching The Darkness
It’s time to finally unearth this mystery by using yet another suicidal plan. It’s all fun and games though as you get to dive into the murky depths with a giant mech to find a hulking beast that can take down a Reaper.
This section is more of a suspense builder before the unveiling as all you have to do is follow the flares that Shepard throws out. Keep walking, following them until you find a ledge to drop off. Keep doing this until you make the biggest drop.
You will find the probe. Walk past it until eventually the ground tremors and Leviathan finally makes its appearance.
Note: The final cutscene dialogue will change depending if you brought your love interest along. The dialogue before you enter the ocean can also change.
You now gain access to the Dominate power. It is a tremendously useful power and can turn the tide of battle at the drop of a hat. Enjoy it.