Inside, there is a campfire near the entrance (left path, requires jumping down or clearing the cave) where the Courier can find a key. This key opens a Very Hard-locked gate further along on the North side of the cave. Behind the locked door lies a significant amount of loot. However, right beyond the gate is an easy-to-miss trip wire which triggers 3 grenade bouquets. This trap is especially deadly, as the grenades are set to drop throughout the tight corridor, and will likely kill everyone in the vicinity. Past the campfire is a grim assortment of skeletons, often accompanied by loot including weapons and ammunition. There are numerous mushrooms on the ground here, making the loot easy to spot.
Once the Courier passes the locked gate, unless he/she were stirring things up inside, that is where you come face to face with the legendary night stalker.
Along with the legendary night stalker, there are roughly 11 other night stalkers in the cave.
It is possible for the Courier to enter and exit the second cave zone without being detected by the night stalkers. After entering the Bloodborne cave, take the way left to a platform. The companions should wait here. Jump down to the dead NCR trooper and get the loot. Before entering the cave with the legendary night stalker, climb the first cliffs on the left side, than few cliffs more up till you get to the platform again. This can be a bit tricky, but achievable.