Vault of Glass Gatekeepers and Relics is part of the final phase of the Raid once you've tackled Gorgon's Labyrinth, platform puzzle and the jumping puzzle but you still have two big battles ahead of you.
The first involves defeating three Gatekeepers - massive Hydra-style enemies - and taking control of two Relics before defending a Conflux against hulking Minotaurs.
How to kill the Gatekeepers
The first concept you need to master to defeat the Gatekeepers - and then Atheon, the final boss of the Vault of Glass - is the two Vex sync plates positioned in the shadow of a Vex time gate on the left and right sides of the arena. The left gate sends you to a red location that most teams refer to as Mars; the right goes to a lush green place we generally call Venus. Mars left, Venus right. Tattoo it onto your eyelids.
Another thing to remember: never sprint through a time gate, always walk. It's not clear whether it's a bug or an eccentricity, but sprinting doesn't always return you to the present, and the failure is disorientating.
In this initial fight, you are going to kill a Gatekeeper in the main boss arena. Then you are going to hold the Vex sync plates so that some of your team can journey to Mars and Venus, kill the Gatekeeper that lurks in each location and retrieve the Relic it harbours, then return and defend a Conflux that springs up in the middle of the main arena.
Depending on the skill level of your fireteam, you may want to retrieve both Relics simultaneously or one by one. We will describe the latter, but if you think you are good enough to do the former then have at it.
The first thing you need to do, though, is deal with the Gatekeeper in the main area. You can do this very easily. When the boss door first opens, linger in the corridor outside and prepare your biggest weapons. The first Gatekeeper is directly ahead of you, so on the count of three, everyone blast him together. If he teleports before you can finish him off, he should be on low health anyway and easy to kill.
With the first Gatekeeper down, everyone go to the left sync plate, which opens the gate to Mars. As you power it up and while you hold it open, Goblins and Praetorians will assail you from two easy-to-spot doorways. Call them out and destroy them. Once the Vex gate is open, send two of your best players through. The four players who remain must hold the gate open by controlling the plate.
The two players who are in Mars are faced with a small arena, similar in layout to the main one, with a Gatekeeper up on the stairs in the middle and Praetorians and other enemies dotted around. Killing the Gatekeeper is top priority. Once it's dead, a Relic spawns at the top of the stairs. Retrieve this and return through the gate to the present.
As soon as you get back, use the cleanse function, because the two of you who went to Mars will be marked for negation. A nasty side effect of this in these fights is that your vision starts to cloud until you are completely blind, so cleansing is a necessity.
At least one player must now go to the centre of the boss arena where a Conflux has formed. Minotaurs will be heading down the stairs toward it, trying to sacrifice themselves. They come in a steady stream but you should be able to hold them off with a powerful shotgun or another weapon with similar stopping power.
Meanwhile, the other five players go to the other sync plate to open the route to Venus. Enemies will attack you while you do this. Once the gate is open, send the person with the Relic and one other person through to Venus to perform the same drill as Mars: kill the Gatekeeper, bring the Relic back, cleanse as soon as you get through the gate back in the present. The Relic holder needs to go to keep both players cleansed, as the marking effect will activate as soon as you arrive in Venus.
Once everyone is back, go to the Conflux in the centre and defend it. Powerful Descendant Minotaurs will assault you from the stairs and from both Vex time gates. The Relic holders are both potent defenders here and should address one time gate each, but keep those void weapons and Supers handy as well. Kill and prevent sacrifices long enough and the Conflux disappears and you're done. Now it's time to take on Atheon.