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[Diablo 2] How did Marius manage to enter the Durance of Hate, let alone without being spotted and killed?

So Marius (somehow) manages to get all the way from Tal Rasha's tomb to Kurast, then to Travincal and the temple.  This seems unlikely for a couple of reasons:

1.  Jerhyn had commanded all ships be docked, and the first ship out sped to Kurast with the heroic adventurers.  It seems, however, that Marius arrived in Kurast before they did.

2.  Entering the Durance requires destruction of the Compelling Orb (or fancy teleportation, which was available to the dark wanderer, but not Marius), something that was not done until the adventurers entered the Durance themselves and killed Mephisto.  When Marius found the three at the Infernal gate, Mephisto seemed to be just fine.  How did Marius get in?

3.  There are hundreds of vicious monsters all over Travincal, Kurast, and especially in the Durance of Hate.  The heroic adventurers had reasonable difficulty getting past them - how would some frail man barely hanging on to his sanity manage to sneak all the way in and out?

4.  At the climax of his journey, Marius is less than 100 feet from Baal, Mephisto, and Diablo.  It is later evidenced that the three didn't particularly care for saving Marius' life, how could the three be so blind as not to notice either Marius or Baal's soulstone which was draped around Marius' neck?


Bonus Question:  When Diablo went through the Infernal Gate, he ended up in Hell.  When the heroic adventurers went through it, they ended up in the Pandemonium Fortress.  Where would Marius have ended up if he actually managed to get through the gate?

Bonus Question 2:  How did Tyrael expect Marius to get through such a well guarded gate with... courage?
gpt
Marius was just before all the fuckery started to happen. Demons comes after the Great Evils, not before it and it takes sometime before people notice that the land is infested with Demons.

Jerhyn closed the Docks when he heard reports of demons out in the sand, hopping to have some evacuation ships when shit got really bad. Marius was just shortly before the reports came in.

Travincal, Kurast and the Durance of hate was empty when Marius was there, the Demons started to appear just after he left. When Diablo freed Mephisto shit got bad in Travincal that that we see.  
How he got in to the Durance of Hate, the same way Diablo did, Diablo probably opened up a alternative door, maybe straight through the ground itself.