When you clear the hill of rubble leading up to the tops of the buildings in the square, you will find a small group of Reapers entrenched in the rubble along the top of the building. To the right of you will be the smoldering remains of the ship that was supposed to take out the Hades Cannon, and strewn among the rubble will be two rockets that you will have to use to destroy the Hades Cannon. For now, though, worry about the enemies who will block your path. You will only be facing Marauders and a few Cannibals here, so this battle is no big deal. You may be able to get a jump on the enemies by killing the first Cannibal or two while their backs are turned to you. If you are playing as an Infiltrator, make the most of this and use Tactical Cloak to get an instant kill on whichever enemy you deem deserving of it.
Other close-range classes, like the Vanguard and the Sentinel, can wade into this battle and use melee attacks and Shotguns to make short work of the enemies. Soldiers should pop Adrenaline before aiming out from cover to pick off whichever Reapers are unfortunate enough to be caught in your sights. Engineers may want to set up a Turret in the spot to the left of the first fallen pillar. If you do this, be sure to allow the ability time to recharge before you take down the Hades Cannon, as you will most assuredly need it again. Dig in to cover and carefully pick off the Marauders after you kill the Cannibals that will make up the tip of the Reaper’s spear in this battle. These may not be the toughest enemies in the game, but they can still kill you if you’re not careful. If necessary, stick to the back of the arena and use your Sniper Rifle to pick off the Marauders who will be lurking towards the back of the area. Also try using powers, like Incinerate, Cryo Blast, and Warp, or even Cryo Ammo, to kill the enemies faster. This works especially well if you aren’t packing the biggest guns. Pick off the enemies one by one before heading over to the crashed ship.
When the other enemies are mostly dead, a Ravager will begin to fire at you from the back of the area, too. Take cover, as its blasts are powerful and can deplete your shield in no time if you are left exposed. Order your squad to focus their efforts on the Ravager. Bring it down to clear your path to the ship for good.
Pick up the M-920 Cain. This one-shot weapon is a powerful rocket blast, almost like a mini-nuke, that you will need to charge up for several seconds before firing. A waypoint will appear right on the side of the Hades Cannon. Fire the M-920 Cain at the Hades Cannon. The one blast should be sufficient to blow it up. As Shepard radios in that the skies are now clear, you should run over to the wreckage of the ship and grab the Med Kits from the flames. Also pick up the second M-920 Cain, as you should have only had to have used one to bring down the Hades Cannon. When Shepard radios for evacuation, you may want to begin charging the weapon. You will soon hear the telltale shriek of a Banshee, and sure enough, it will appear straight back, towards where the Ravager came from.
You will now have to survive until the Alliance can reach you position with a dropship. Let the M-920 Cain fly directly into the Banshee when it appears, and stand back and watch as the entire back of the battlefield goes up in smoke. You will have just cleared your most significant hurdle during this next battle with just one shot. The rest of the approaching troops will be made up of Cannibals and the occasional Marauder. If you were able to take out the Banshee with the Cain, you should dig in to cover towards the wreckage of the ship and take potshots at the enemies. They will quickly approach your position, though, so don’t hesitate to switch to a Shotgun and gun a few down if they get too close.
Fan your squad out across the cover in the back of the arena in order to keep this flanking maneuver from happening too often. With one squad-mate to the right and one to the left, you should be able to get a pretty good killzone going towards the back of the arena. No matter how many enemies you kill, though, more and more will just keep spawning. Grab the ammo from where it sits on the various cover positions on the rooftop to keep from running out of ammo in the gun of your choice. Using Assault Rifles, SMGs, or Shotguns is recommended in this section, as the enemies will get too close too fast to make sniping feasible.
When the dropship finally does arrive, you will have one last thing to worry about. Since the enemies will spawn infinitely, the distance between your cover towards the downed ship and the safety of the dropship can be a deadly one. Climb over the cover and sprint as fast as you can towards the ledge in the back. When you reach it, just keep running and Shepard will automatically jump across and into the dropship. Sprinting alone can be deadly, though, especially if you weren’t able to kill the Banshee right away and are low on health now. Sentinels should use Tech Armor to beef themselves up before making the dangerous run. Vanguards can use Biotic Charge on a nearby enemy to cut the distance in half, while Infiltrators can use Tactical Cloak to make the journey in relative safety. Adepts should use Singularity, Warp, or Stasis to render as many enemies as possible harmless, then sprint over, while Engineers should set up a Turret in the back to take the heat off of themselves and to provide cover while they sprint towards the dropship.