In the warpgate area of Endless Gate, the player is able to venture outside of the intended playable area. It is possible to transverse the small platform behind it and see other areas of the map. Jumping off of the platform results in a death. Apologies for weird crops, Steam didn't agree with me exporting screenshots, so I had to screenshot the previews and crop them myself.
https://twitter.com/Piratepatchy243/status/816053684505350144?s=09 Not the first out of bonds area and won't be the last, honestly it's fun to find this type of shit and has been a thing since D1. Shit I like doing it to get good screenshots, like the Templar area in VoG and WotW quest area. Unless it provides an unfair advantage in PvP or abnormal access to gear I see no issue with this.
There are hundreds of these places in the game. Archers Line on the moon straight up has a hole in it you can fall through where a structure meets the ground.
It ain't a new area Looks like that one Hive Queen related Strike Festering Core