The Gorgon's Labyrinth is home to two loot chests and a load of white, Harpy-style enemies called Gorgons who will kill your entire fireteam if they spot you moving among them, and comes swiftly after finishing the Templar boss.
After that is a jumping puzzle, which is a deceptively fiendish descent towards the door of the final boss arena.
The Gorgon's Labyrinth
If you reached the labyrinth by going through the main door at the back of the Templar arena, you won't have found the first loot chest yet, so let's help you out with that.
Standing knee deep in the murky water at the bottom of the massive fall that led you here, go left and look high up the wall. You should see an opening that you can reach with a few well-timed boosts. Head through there and you should easily discover the semi-circular Vex door that leads to the next loot chest.
If you came in through the secret exit from the Templar arena, you should have found this chest quite easily. However you got here, once you have the chest, exit the room and find the way down to the swampy floor of the main labyrinth.
To find the second chest, bunch together and work your way through the labyrinth favouring the right wall. You will have to go a little way through and dodge the odd Gorgon - you only need to avoid direct line of sight - but you should find it quite quickly. Once you have the loot, retrace your steps back to the start of the labyrinth - or just present yourself to a Gorgon, wipe and respawn.
To find your way out of the labyrinth, proceed forwards to the left of the large triangular rock in front of you that looks like a ramp. There are Gorgons scattered around, so be careful. A little beyond it, take a 90-degree left through the large opening on one side of the main area and go directly across the large cave you enter, over the cluster of rocks and straight ahead in the direction of some concrete and bright lights. As soon as you have a wall on your right side again, hug it - you should drop down into a sort of ditch - and keep hugging the right wall until you find an opening. This leads into a cramped but well-lit passage that leads you out of the labyrinth.
How to kill a Gorgon
If you've been spotted by a Gorgon, then you've probably tried to blow it away and failed. Tough, aren't they? There is a way to do it though, if you're quick and very powerful, and doing so gets you a Grimoire card you might otherwise never obtain.
The trick - it's not much of a trick - is simply to pile in as powerfully as possible in great numbers. Hit the Gorgon with every Super you can, rockets, machine gun fire and grenades. Between the six of you, you will take it down and get that Grimoire card.
Beware, though, that the Gorgons become more powerful when one of their number is destroyed, locking one of the chest locations. (In other words, do this last.)
The Vault of Glass platform jumping puzzle
In theory this part of the Raid is straightforward, but in practice you may need a few attempts before you make it to Atheon's door. Remember: if you're in a fireteam with someone who is struggling, you can always jump into the abyss and respawn up on the highest platform again to give them a helping hand.
The idea is that platforms spawn in midair in a predictable sequence, vanishing just after the next platform appears, so you need a mixture of good timing and good memory to descend in the right direction at the right time.
For most players, though, it's only necessary to use the first two or three platforms before relying on your class's double and/or triple jump ability to make it the rest of the way. From the second or third platform, launch yourself towards the wall diagonally ahead on the right side of the cavern. There is a narrow ledge running along the middle of it that will catch you and let you hop along to the boss door. To avoid missing it or dying of fall damage, save that final burst of Titan boost or that final Hunter jump to catch your fall.
Once you're on the ledge, move carefully along it and watch your step - shaved edges and jutting corners will send you into the abyss if you're not careful. It's a good idea to treat each undulation as a threat and jump around it, working on the basis you may need to jump to save yourself at any time.
At the end of the ledge, drop down, group together and head down the corridor towards the triangular door with a big 'A' on it. Next up is a section involving Gatekeepers and Relics.