You can drop down and walk on these, under the bell and straight into the boss fog door (which does at least look like it fits in the surrounding aesthetic this time). When the cutscene clears you’re exactly where you were, but everything is rainy and windy and there are a lot of dark clouds in front of you.
In front of the bell is a lever pulling it triggers a cutscene and a sudden storm. On the right is a large bell, which is probably why this area is called the Great Belfry. To find the Nameless King’s boss fight you need to start from the Great Belfry bonfire and run back along the corridor. Luckily he’s totally optional, so you don’t actually have to do this one. This guy is worse than Pontiff Sulyvahn and Aldrich put together. We can help you prepare and tell you want to expect, but honestly, this fight mostly depends on how well you can learn his attack patterns and time your own movements accordingly. His attacks have a huge hit box, whilst the hit box around him is tiny given how erratically he moves in the later stages of the fight. Alright, we’re just going to say off the bat that the title of this guide is a bit misleading, because there is no guaranteed way to beat the Nameless King.