[spoiler] the grottos is an area just off the shipyard area, small valley off the water front. Right side of it if you're looking at the water. can't go very far due to level?? Fallen[/spoiler]
[spoiler]So I went back there, to the grottos, and decided to try pushing past the level ?? Guys. I made it past a big section sneaking/running past a bunch of guys, went thru a hive cave, and found myself in the map for the devil's lair strike to which I could freely roam and die without starting things over. You can kill the devil walker with as many deaths as you want. You can't go thru the door after him tho. I then backtracked the strike map and met up with people in that middle area of the strike. I assume they were actually in the mission and I was just passing thru. Just insane to think I might have been some random person they passed by in the middle of their long mission designed for a 3 person fireteam.[/spoiler]