*All directions given in the guide are oriented from the elite's perspective*
This is easiest to do on the spire map. I got this achievement in my first game of invasion using the roll elite guide below.
When you get a game and start your turn to defend as the elites you have two options, a camo elite or roll elite, I think the easiest to get this achievement is with the roll elite.
Spawn in and grab a needle rifle from around either area you defend, then make your way to the road in the middle of both areas. You want to wait around the area on the left. Here you will use your roll to scope out the road left of the area, the area itself, and the middle road. Doing this will give you great intel into what is happening in terms of the enemy attack route, allows you to stay alive, and allows you to grab the ammo from the needle rifle that spawns at the rock on the left side of the entrance of the area. If the enemy attacks the other area, you check for enemies near your area, stay and defend if you have bad teammates, or are alone on this side, if not, then go through the tunnel to defend. This works best with a decent team, decent partner, a bad opposing team, but also if you spawn on the left side. *Stay behind the left area, never push forwards, only side to side for sights, and through the tunnel to the right area.*
Only do this if you spawn on the right side. On the right side of the map is a cliff with a big rock, this rock has a tunnel in it that spartans use to come through or go around on the cliffside. You want to wait on the rock in the middle of the tunnel and the outer route standing still or crouched to hide your radar. When spartans show on radar activate your camo. Make sure to follow the spartans red dots on the radar and don't get confused by your own camo's shield jammer.
If you are good enough and sneaky enough, you can get lots of assassinations, disrupt the spartan attack by back shots or confusion from the shield jamming. You and your partner alone can usually hold the right side alone if he cleans up from on-site with a needle rifle. Once your team sees you are holding the right on your own they usually pile onto the other site and can usually hold it.
Counters to these strats:
-Spartans are aware of the camo strat and some players will attempt to counter you at all cost, but this usually means they cant really push the area effectively unless they kill you early, or they all pile on the one side.
-Some spartans will sit on top of the camo rock and fire into the area with their pistol and will have their partner spawn and attack continually from that spot. If you are camoing below you may not see this on the radar, and cannot counter this player, your team needs to needle rifle them or hide on-site, which leaves you isolated and vulnerable to the spartans strat above.
If this fails, you can always create a session here and get a good group together to try and get this. My guide was mainly for solo players or two-player groups. If you make a session here then breakpoint is probably going to be the easiest map. Boneyard needs a good team to defend the start against even decent players as the forward partner spawn of the attackers is very strong on this map, and basically doesn't exist on breakpoint.