Echo's Beacon is a boss fight against Raging Raven. If you trying to kill her, now is a good time to use the FIM-92 Stinger missile obtained in South America. If you're going non-lethal, The Mosin Nagant is the only non-lethal weapon that can really reach her. Raven will strafe with her grenade launcher, send UAVs after you, and generally pound the entire area to smithereens. Her main weakness is that she can't find you easily, so use OctoCamo (along with the face mask) to maximize your camouflage. Stay away from her UAVs, as they are capable of spotting you more easily than she herself is, and furthermore they each carry a fairly heavy missile payload. Take them down with a silenced M4. Change floors occasionally to confuse her. On the lowest floor, she'll come in and hover around, and you can hit her with close-range weaponry like shotguns or machine guns. Up above, the walls are much more fragile - stay away from them. At the very top, there's a small angle, a corner next to the stairs, that won't break apart and that she can't hit you from. If you don't mind being a little cheap, you can use that angle to hide in whenever she counterattacks. The main problem in this fight is probably lack of health, since you came in from the last motorcycle battle.

Try to conserve your health and hide to regenerate if you start to get low. Use the Solid Eye to note where she is and where her attacks are (the bombing runs in particular will show up on your Solid Eye as a group of circles). If you find yourself constantly under attack, head to the top floor and launch guerilla attacks on the UAVs. They're the primary thing showing her where you are, and as such should be your main concern. A lot of weapons pretty much bounce off her, so this is going to be a painful battle of attrition whatever you do.

So there's a couple different things that will happen in this fight. On the lower floor, it'll mostly be her sending her UAVs in looking for you. Hide on the staircase and pick them off as they fly by. On upper floors, it'll be mostly bombing runs, so keep your head down. A lot of times, she'll overheat and either hover there panting heavily or fly off to a building in town to cool off. Either one is a good chance for a shot at her. If you want to tranq her, a Mosin Nagant round to her head in this section does the largest chunk of damage I've seen anything do to her. The last major thing that will happen is Raven launching a bunch of missiles at you, so when you hear beeping just run. You can't dodge it by hiding in the usual manner, so switch floor or something.

So, to sum up: stay away from and shoot down the UAVs, then take her out. Move from floor to floor to mix her up, and hide every so often to confuse her. The biggest pain is that everything that shoots at you in this fight does so with explosives, so you'll get knocked around a lot even if you dodge the initial hit. However, once you learn her patterns and take down her UAVs (she replenishes them slowly, though) this fight isn't that hard. The faster you move and the faster you aim, the less of a problem this will be.

After the fight is her Beauty phase. Take her down lethally or non-lethally. If you tranquilized her in the first part, her figurine is on the top floor, on one of the corners. She'll have her ending animation, you'll pick up her grenade launcher, there'll be a bunch of other cutscenes, and that's the end of part 3.

Metal Gear Solid 4 Walkthrough