When most refer to the difficulty in a Dark Souls 3 game, they're usually referring to the various enemies throughout the game that are more than ready to tear you apart.
However, many forget that the environment itself can be just as treacherous as the enemies at times, featuring poisonous swamps, lava, bottomless pits and all sorts of traps just lying in wait for anyone who starts to find themselves getting a little too complacent.
Unfortunately, most of the game isn't optional, and many of these dangerous locations throughout only serve as segues to another location. The Cathedral of the Deep is one such place, with its only real purpose to have players traverse it in order to get the "small doll," which is needed to enter Irithyll of the Boreal Valley at the end. However, now, it's possible to skip through that annoyingly long dungeon and head to Irithyll of the Boreal Valley directly, thanks to a recently-found glitch.
YouTuber PeachyMike has found that it's possible to bypass the entire Cathedral of the Deep by using the Tears of Denial miracle. As such, before you can even attempt this glitch, you'll need that miracle first. To get it, free Irina of Carim from her prison in the Undead Settlement and give her the Braille Divine Tome of Carim from the Road of Sacrifices. Upon doing so, she will sell the Tears of Denial miracle for 10,000 souls.
After purchasing the spell, you'll need to follow a few quick steps:
Step 1: Abyss Watchers
Step 2: Complete the entire dungeon (don't forget to cut down the rope bridge in front of the boss room before leaving) and head to a ledge with a tree directly below it (in usual circumstances, a good marker would be the stairs directly to the left of you, but now, a better marker would be all the bloodstains around it).
Step 3: Cast Tears of Denial and drop down to the tree mentioned in the previous step, move ever so slightly to the right and then drop down to the rocks directly below.
Step 4: If done right, you'll fall through the rocks and find yourself on the ground below. Maneuver your way through all that until you reach solid ground, then quit and reload the file.
Step 5: After reloading, your character will appear near the moat area (and with the proper third-person view), where you can head on over to a nearby bonfire — granting complete access to Irithyll of the Boreal Valley and allowing you to completely bypass the Crystal Sage, the Deacon of the Deep and the entire Cathedral of the Deep.
Do note that none of the sections of the game that this glitch lets you skip are particularly hard: the Crystal Sage and Deacons of the Deep boss fights are some of the easiest in the series, while the layout of the Cathedral of the Deep seems to be designed to just annoy players until they make a dumb mistake and die. The true value of this glitch is that it allows players to skip those annoyances completely and head straight into the middle of a later section of the game — something highly desirable to speedrunners.
Of course, there are some downsides to the glitch. Skipping the Cathedral of the Deep means no Lloyd's Ring (one of the best rings in the game for skilled players), and failing to execute the glitch properly could lead to losing some of the time the glitch was intended to save. Either way, Dark Souls 3 speedruns just got quite a bit faster.