Cornswantz Seabeble-bop was a wizard obsessed, obsessed with extra-dimensional spaces. He was constantly experimenting and studying them, trying to probe and understand their mysteries to see what other applications could be made from a dose of "extra" space. After a presentation to the nobility and military forces on the potential of extra-dimensional fireballs, Cornswantz was able to build himself a research facility to be able to best conduct his experiments without being dangerously close to other living souls, in case of catastrophic rupture, a constant professional threat. It was at this research facility that his most important discovery was made.
Ever trying to grasp the incredible dimensions of "extra", Cornswantz hired workers, researchers and explorers in an effort to fathom the boundaries of "extra" space. Bag spelunkers, or "B-lunkers" as they were known, were brave adventures on the brink of sanity who descended into the various bags Cornswantz possessed and explored the properties within, only occasionally coming back alive, or with any sanity left. His best team of B-lunkers was known as the "Ants team" a collection of people of small stature with amazing strength and constitution, able to carry the supplies needed for extended missions without the use of extra-dimensional spaces within the extra-dimensional space they were exploring, for obvious reasons. The Ants team was the first and overall most successful team in "mapping" extra space, although it was not so much a map as it was an extensive and mentally daunting math equation.
Using the new found knowledge of the Ants equation, Cornswantz was able to create a new class of extra-dimensional spaces, far more powerful than previous bags of holding and portable holes. "Nothing holes" were able to create exit portals ten feet away even in the absence of something to put a hole through, simply creating a hole in space itself. "Sacks of holding" were simply alternate bags of holding, but created with a different base equation, so actually were able to exist, sack inside bag or bag inside sack, without ground shuddering explosions. Only about a dozen of these sacks of holding were off site when Cornswantz first experimented with his "Extra-Dimensional Bag" and changed how extra dimensional space was thought of.
With his lifetime obsession with extra dimensional space, unique knowledge on its finer points and own pioneering work with new equations for sacks of holding, Cornswantz was able to "run the numbers", so to speak, for extra dimensional space, and came up with an new equation that he initially discarded as a failed work before it's nature became a new obsession within an obsession for the already mentally strained wizard. In layman's terms, the equation divided by zero.
Now, to get a better grasp about what that means, think for a moment how a standard, so to speak, bag works. You put something in, it goes somewhere else, and you have room to put more stuff in. Portable holes basically work the same way in reverse, moving the stuff in the way to somewhere else, and letting you move things through the absence of stuff. What dividing by zero meant was when you would reach in, you would be grabbing the stuff around you, and moving it somewhere else.
Cornswantz was excited at the prospect of traveling through extra dimensional space, and with most of his B-lunkers either retired or dead, and the Ants team still missing, Cornswantz decided to craft his first, and perhaps only, extra dimensional bag for himself. Even for a wizard, he was a puny figure of a man. A lifetime of devoted study and sanity eroding math had left him a wisp of a man unable to carry a single one of his own resource books. That isn't the best measure of his strength however, as most men could not carry one of Cornswantz's books, they often weighed as much as several children. In the enchantments for his bag, he added a spell to allow him to move things at a magnified rate, so he would be able to lift himself and a small wagon full of supplies he deemed as being necessary to travel through extra dimensions. The spell was not one of his own, however, and from the results, it was determined he either had a poorer self image than expected, or overcompensated for the spell several times over.
Cornswantz reached into his extra dimensional bag. Searching around, he felt and recognized his own robe covered back. Grabbing a handful of robe and pulling, the wizard, the wagon, and the entire facility around him were pulled through the bag and into another dimension. A vast, perfectly hemisphere of a crater remains where the facility stood, surrounding earth slowly eroding down into its maw, a testament to a man obsessed.
Some say he'll be back someday, once he masters his new equation, others say he died and destroyed his entire facility in some kind of reverse explosion, still other say he never left and their own extra dimensional bags work fine, but those are the guys in the sanitarium. Cornswantz Seabeble-bop was a man of vision, a man of exploration a man that could reach in and pull himself out of a hat, and his works live on past him, forever changing how people use extra space.
If the players should ever actually find the facility and the bag, they will have a transportation device, that will allow them to pull themselves and a small area around them to another dimension. The strength enhancing spell as worn off somewhat over time, so they won't be pulling acres of land along with them. Where they go, and if they recognize it as being different dimension than the one they just left, is up to the DM.