Endless Dungeon
i think it is called “Fractals”
but solo mode is nice idea.
I think what the op is imagining is more like hardcore endless waves/rooms and when you wipe you’re done. Or not necessarily hardcore and a wipe = game over. So it would be like path of mobs, boss, path of lvl2 mobs, lvl2 boss, ect. til you/your group quits.
While the fractals is similar it’s different since you can start at any level you want. I imagine an endless dungeon starting at 1 every time and going til you stop. Or if it was solo hardcore it can save your process til you dies so you can take breaks. Fractal is also very puzzle/goal oriented while dungeons are not usually, dungeons are more just fighting mobs and bosses.
Ooooorr could just being saying BS and the op wasn’t aware of fractal and how they work. Regardless it could be a neat addition as some LS story thing like SAB or a normal addition to the game called “The Training Hall” or something.