I've heard the word Underfoot several times from the lore. Is Underfoot a seperate dimension/planet or is it a deep underground area in Norrath?
Its both a separate plane and a location. Please note that what I'm about to say is based upon a lot of lore and research but none of it is exactly canonically stated. Its more implied/visually displayed, etc. Some planes of existence are closer to Norrath by their very nature than other. Growth, Sky, Ground/Underworld and likely even the oceans. These planes are naturally tied to their elemental or orderly existence and so they are actually anchored to Norrath. That's why you can walk into these planes. (Other planes are tied to Norrath like fear, but those were because specific portals or doors were put in to facilitate this.) The door in The Hole was the result of a magical explosion that shifted part of Norrath to Luclin. You can kind of see it as being unnaturally created due to the closeness of the planes at that depth. The border from Underfoot to underfoot or from Plane to underworld is in the depths of Thalumbra. The "walk in" doors between Sky and Growth most likely got damaged in the Rending (or potentially as backlash from the cataclysms that shook Norrath). There is still bleed over, however. The kingdoms of sky, the massive growth in Velious, etc. I'm pretty sure the same is true of the Ocean but we really don't see much of Prexus in either game. Probably because most knowledge is filtered through land dwellers who treat the sea as if it is insignificant.
You're talking about "The Shifting", as the Vah Shir called it. It was the Ulteran Teleport experiment that sent an entire section of Stonebrundt Mountains and the Vah Shir home city up to Luclin. During the Erudite Civil War, the heretics of Paineel ended up exploring as deep into the hole and discovered the portal to the Plane of the Underfoot. The elementals that emerged from it were too dangerous for them to handle, so they decided it was best to physically close off the portal.
Thank you for the correction, Cusa. My brain knew I was getting something mixed up but I couldn't, for the life of me, figure out what it was.
Found a little more too about the underfoot. I guess both Brell's plane and Veeshan's border all of Norrath in their relevant sphere. This is from the EQ2 website, some of the lore they gave us in the past.
