You went through it to get to Shadowlands, and now you’ll be going back there on a regular basis. You get to it from Oribos, the level with the flight master—just jump into the opening in the center of the ring. Each Covenant will send you into the Maw once a week to rescue souls. When you’re on that quest (and have the “item” from Ve’nari) the minimap will have little white “running man” ghosts on it where souls can be found. You don’t have to go too far from where you land to find souls, they are scattered about. They are often trapped in stone prisons that you have to break to get them out. Right click on the little white souls to collect them. In some areas of the maw, the souls have exploding/stunning swirls around them; you can still collect them, you just have to be quick about it. Some stone prisons don’t have souls in them, use the minimap to find the ones that do.
Everything you need for the Covenants can be found in the initial part of the Maw. There are two areas that can only be opened after building up reputation with Ve’nari; they typically require groups to survive in.
There are always two daily quests available in the Maw, shown by the usual blue exclamation point. They give you extra stygia (the currency of the Maw, in your currency tab) and rep with Ve’nari. There are a host of special mobs that also give bonus rep and stygia, you get a quite clear announcement when they are near, and can be done daily. There’s also a “world boss” (Wrath of the Jailer/executioner) that shows up and can be done once a week. You’ll see crossed swords on the map when it is about to spawn, then a warning when it does pop. It is rumored it drops gear, I’ve never gotten any. There is also a weekly quest (yellow exclamation mark) available from Ve’nari, as well as quests related to story/rep level with him.
Your time in the Maw is limited each day by the Jailer’s Eye, which is well explained the first time you are in there. Levels 1 and 2 are not bad at all, 3 with its assassins is annoying. If you’re trying to build up rep with Ve’nari fast you’ll go higher, consult an advanced guide.
There are some fast travel options you can unlock. When you kill one of the mobs mounted on the mechanical bears, you can ride it for a short time. There’s a portal in Ve’nari’s refuge you can unlock to take you to the far west of the map, and another unlock that moves between two different pairs of pillars (riftstones). Ve’nari forces an item onto you that ports you back to him, it’s the best item in there.
If you die, you resurrect at the equivalent of a graveyard. You are not a ghost! About 20% of the Stygia that you had is still on your body where it died, so you want to make your way back there to loot it…but be careful. If you die again on the way back, the stygia on the first body is lost, and it’s now the second body you have to get to.