It's simple, really. The curse-field is present in most parts of the abyss, and becomes thicker as you go deeper or closer to the central column. However, you only begin to suffer the effects if you go against the field, i.e. go upwards.
Once you get deep enough, the strain of ascending becomes so harsh that it'll kill you, or take your humanity, or worse. So, of course, those who wish to delve deeper either don't come back, or devise a way around the curse.
Deflecting the field isn't too hard, but unless you give it somewhere to go, it'll merely delay the effects by a few seconds, so you need to give the field something to sink into. As it turns out, the only thing that actually absorbs the field is consciousness. So you need to bring a friend along to share the burden with you.
tldr; the first one's an edit and the second one isn't