I'm afraid the original post was gibberish to me
I'd love to translate it, but I'm not sure if direct references to drugs go against UKCaving guidelines. It is something along the lines of
'My friend and I have decided to tackle the Chamber of Horrors, and in between the ducks we will smoke a green leafy thing to make the experience more comfortable'
'Hotboxing' is when a substance is smoked in an enclosed space so that the smoke fills the air and accentuates the effect. Obviously I'm only talking about tobacco here...
The arrows on the ceiling are 1) a reference to the blue arrows that were painted in the passage in giants just over a week ago despite there being no obvious turnings in the passage, and 2) a joke because there aren't exactly a ton of passages leading off CoH.
The joke being that obviously, hotboxing CoH (this would have to be done when at least the 3rd duck is sumped, so there is less draught) would be a stupid idea and may well lead to drowning and / or hypothermia. It is nevertheless an amusing scenario to envision. The idea of having a rave in CoH in general is just somewhat comedic to a poor lockdown soul that has not left the house in 5 days.