There’s a few quick tricks help you get through Devil’s Lair quickly. Hop on your sparrow and run down to the first area where you have to fight the three waves. There’s two great spots in the back corner. On the top level you can hide behind the big shipping container. You can also hide on the bottom level. When each wave comes, pull out your sniper rifle and take out the vandals sniping you from across the area. Then take out the small unshielded guys. Save the shielded captains and wizards for last because they will try to run away. Keep an eye on enemies jumping up to your level. When you get to Devil Walker stay in the back on the top of this building. It’s very difficult for the walker to hit you when you stand behind these pipes.
Just keep your eye on the radar because a captain and a vandal spawn on the right side. Wait for them to jump up and blast them away quickly so you can get back to taking on the walker. Shooter the walker legs with a rifle, then switch to a sniper to shoot the core when it’s exposed. Also keep an eye for a vandal sniping you from this ledge. At Septiks Prime, hide in the entrance area and shoot Prime from here.
When he fires purple balls, just duck in and out as you deal damage. Keep a super charge and a grenade ready, because shielded captains will spawn around the entrance area. If it’s on a higher difficulty you may want to duck out in this garage area over here because you are protected from both the smaller enemies and Septiks Prime.
As found on Youtube