On the hoard mode after destroying all the crows You get small series of beeps which then refer to the bricks in the wall on the bridge as the beeps are in binary ( dots and dashes , 1 & 0 accordingly) , me and a couple people heard "the wall" being said by a croaky feminine voice so we then associated it, we just need to figure out the next step and what it leads to, we also dont know if it is the wall on the bridge or the door as they both stick out to us, we are about to try the door, will keep you all updated. we could not get this to happen on anything but hard.

Edit - this is to be done on the door you are trying to defend and it seems like mcree needs to do it, or atleast thats how we managed to get it to be done, there is a small hum whilst doing it, saying your hitting the correct parts. the voice said "the voices are not what they seem, make sure he doesnt die" we are trying to figure out what this means now.

Edit 2 - after 2 attempts first of all, dont keep junkrat alive. but what we decided to do was keep was only keep reaper alive, after a while he went into the water which triggered a dialog which said "find the gift he gave to me" at least thats what we think the voice said as it is very distorted and is mumbled. we dont know what to look for or do now, does anyone have any ideas

Edit 3 - the hanzo in our group shot the rings on the electro pylon on the tower, and we heard yet another humming noise but this time it was louder followed by a "thank you, now wait" this time also clearer, we dont really know what to do now so we are just going to sit around in our current game and of course will keep you up to date. Please let us know if you figure anything out.

Edit 4 - Ok so after waiting roughly 5 minutes the game just ended into the usually win screen. So we tried again, after repeating all of this we shot the other towers with progressively louder humming noises, after we had done this we all heard a voice (instead of just one of us) saying "you will be rewarded", we think that this is the end but we will keep on searching, and i will keep you all informed.

Edit 5 - We went on to shoot all the pylons from left to right, all of us. This time no humming noise, after we did it we heard a quiet voice saying "find Athena, contain her", we are not really sure how to contain Athena or what to do as she/it makes no appearance on the horde mode map.

Edit 6 - we started randomly shooting the towers which is when we heard 3 short spurts of static followed by "Over watch initiative successfully infiltrated, Protocol sombra successfully initialized. Expect full execution shortly" we are pretty sure then is the full easter egg but we will continue to search.

Note - Due to kapalka also trying it, we are not sure when this has to be done as we attempt it every time in the final stage. Note 2 - We feel like the contain her part of it is just basically saying she has been contained in one of the towers and maybe the previous voices were recordings?