I trust nothing you say. I'm taking the portal beneath Spellhold instead.
Yes, folks, I'm starting this thread because I
don't have an idea, I only have an
idea for an idea! I suggest that we try to think of an alternative destination for the portal that nobody has gone through for the past 7 years. Now, because Irenicus & Bodhi chose to go through it, it must exit somewhere relatively close/convenient to Ust Natha, but it could still offer the player a viable alternative to visiting the Sahuagin City (and the powerful items & big chunks of quest EXP contained therein). New map area? Almost certainly. But what sort of place would it be?
Another of Irenicus's secret laboratories, perhaps constructed before his fall, and revisited now because it also contains a portal that leads to the Underdark?
Some kind of magical nexus, like Ice Island from BG1, that he visited in order to obtain something that would enable him to steal Adalon's eggs?
Some relatively isolated place on the surface of mainland Faerun, visited simply because a surface entrance to the Underdark is nearby?
Irenicus works with (a few) Rakshasa during Chapters 6/7 . . . might we visit a headquarters of these Rakshasa (even though they don't work well together)?
Do Githyanki wizards disrupt the portal's magic and yank the party out of the ether prematurely, in order to win back the Silver Blade, and the party has to (a) beat the Gith and (b) "reboot" the portal to get to where they were originally headed?
Related bit of weirdness: Suppose that, in this new destination, the party is able to obtain the blade of the Wave Halberd. As players, we all know that this would create a logical impossibility (barring things like time travel & whatnot), as the blade would have to be in two places at the same time. But as
characters, anyone who obtains one copy of the Wave Blade could have no knowledge of the existence of the other Wave Blade, so the only incongruity would come from out-of-character knowledge. The mind-screwiness of this poser amuses me, and I would be inclined to favor the two blades, because I like messing with people's heads.