Just found a new trick, well, not JUST but recently. You can be on any difficulty, and the level has to be Regret (This works better on single player, i dont no why). 1st, do the level up intill you have owned the hunters and the lift has showed up, kill the covent on the lift and pick up any weapons you wanna have, then find some PLASMA! nades and walk to the edge of the lift facing the temple were the jackles were. Now read closly, through the nade so it stays on the very edge of the life. Then about 2 secounds and then jump towards the building, if this is done correctly you should land safely on the building. Its pretty dark, so use your flashlight. Theres not much over there, and you can get up to the higher levels, but that isnt worth explaining.
Skull-Seeker95 4 Life!!!!!