The Mystery of the Gate requires the Sputnik skull enabled before starting the walkthrough (a Sniper Rifle would help too). Go to Delta Halo on any difficulty and progress until you get to the part where you must go down the sloping ramp into another level. Get close to the door, and Grenade Jump to one of the ledges on your left or right, then grenade jump again to the top of the building. Make your way across to the opposite side, where you will have to grenade jump to the platform below (this is the spot where you would fight the Hunters). Go to where the Gondola would dock and zoom in and look slightly to the right; there will be a floating switch.
Any enemies that you encounter on the way, except the first two Jackal Snipers, will not be able to see you.
The High Charity ButtonEdit
There seems to be another gate on High Charity. There is no way to reach it since it is floating some where in the room were it is located at.
There are also mysterious triangles, hidden in Halo 2, that are rumored to be connected to the mystery of the gate. There is one outside Delta Halo, one outside Cairo Station, one outside Terminal, several in and outside Outskirts (although these could be graphical glitches) and one in Metropolis. There are various videos on YouTube, some of which are linked below. They may be connected to the spawn points for the secret skulls. It is possible though unlikely that they are actual gates. They may just be graphical errors, or one of Bungie's favorite shape.
- Main article: Halo: Combat Evolved
There has been a YouTube video claiming there is a tri-gate in the level Keyes; it showed the player by the Proto-Gravemind looking down the ramp, and it showed a black triangle on the floor. There was another one close to it right by one of the doors.
- Main article: Halo 2
In Halo 2 there is a big triangle underwater in the level Delta Halo right under the second ruins on the level. On Metropolis there is a small triangle under the door that leads to the docks behind the building. On Cairo Station there is a triangle on a blue window, and this can be seen outside of the level. On Outskirts behind the Pelican you can see a black triangle. Right by the Blind Skull, if you look at the left corner, there will be another black triangle and some people say that if you throw a grenade by the triangle next to the skull, it will go out of the triangle by the Pelican. There is also a gate on The Great Journey at the end of the level where the Scarab breaks down the door. To the right of where it stops moving is an alcove where the gate is. It is unreachable in a banshee (unless you ) due to a barrier. If you stand on the Scarab's leg as it is moving, it might launch you into the alcove (or kill you). It is possible that this gate leads to a Phase Pulse Generator because, like on Installation 04 and Installation 08, the door is on the side of a canyon located right outside of the control room.
- Main article: Halo 3
There is also a newly discovered Tri-Gate in Halo 3, way outside The Ark. Many saw the shape as an Infection sign or a Prophet or Master Chief's face, due to the different perception of different players.
On the Campaign level The Storm, and there is a simple way to get out of the level, either by getting crushed by the scarab or grenade jumping from the platform where you find the sniper rifle during the scarab fight, to get out of the level, revealing three mysterious gates.
Another Tri-Gate in Halo 3 is the one on the The Covenant. It is on top of the third tower and the only way to get to it is by getting out of the map with a Hornet or Banshee and performing the Time Travel Glitch.
Halo 3: ODST
- Main article: Halo 3: ODST
On the map Uplift Reserve in campaign, there is another trigate outside of the map towards the end of the mission. This trigate is very similar to the ones from Halo 2.
- Main article: Halo: Reach
On the mission ONI: Sword Base, there is a tri-gate hidden inside the mountains far outside of the map. It can be reached by using Armor Lock to ride a phantom out of the map and walking into the mountain. This tri-gate looks somewhat similar to the one in Halo: Combat Evolved.