Chris Perkins has revealed that the obelisks scattered throughout various 5E adventures published by Wizards of the Coast was originally supposed to play a central role in the Vecna: Eve of Ruin adventure capping off Fifth Edition. Many Dungeons & Dragons adventures published for Fifth Edition featured mysterious black obelisks. These obelisks were revealed to be capable of time-travel and were tied to a mysterious group called the Weavers as well as the Netherese Empire. In Rime of the Frostmaiden, it was revealed that Vecna had obtained one of these obelisks and it was hinted that Vecna would use the obelisks in his plot to rewrite all of reality.
Vecna's possession of an obelisk was never followed up on, but it was apparently supposed to be a plot point in Vecna: Eve of Ruin. In a recent interview with Polygon, Perkins provided his vision for Vecna: Eve of Ruin. "The original plan, in my mind, was that we would actually culminate the story by going back in time to fight the Netherese Empire,” Perkins said. “It was always on our radar to bring Netheril back in some way. And this was the way I envisioned it happening, because the only way you could really fight Netheril again is to travel back in time."
“I was excited about the idea of a time travel adventure,” Perkins said later in the interview, “simply because it would feel very different from the other campaigns we had done up to that point. And I thought given time and attention, we could do some really fun things with Netheril and explore a style of magic that felt different from contemporary magic. Expedition to the Barrier Peaks would be sort of like the vibe I'd go for, where the magic is so weird it almost feels technological.”
Unfortunately, plans changed when Perkins' role at Wizards of the Coast shifted in his latter years with the company. “The reason it was dropped was that different people were in charge of the adventure design,” Perkins said. “I had rolled off a lot of my hands-on product work to help out with other parts of the business. And so, when I creatively walked away from the day-to-day adventure creation, we sort of lost the plot.”
Polygon has been periodically publishing interviews with Perkins, including an introspective on Rime of the Frostmaiden, and some insight on 5E's adventure design.

