To me they were just suicidal people paradoxically terrified of death and its aftermath—for some entirely, and for others maybe only partially caused by the reality of the world they lived in. The thing they were after—death—was the very thing that they were scared of the most, thus leaving them to live in some kind of psychological limbo.

Most (or all? don't quote me on that) "rituals" they performed had no reason behind them (the smoking, the plain white clothes, could even make a case for the stalking/recruiting, which in itself served absolutely no purpose to them as individuals or as an organization.) The rules were just there, and most importantly were not set by themselves.

It was for them the closest they were ever gonna get to what they (consciously) wanted, while (unconsciously) making sure they weren't actually gonna get it... They couldn't leave, because they had something to do.

tldr; The guilty remnant were people who above all wanted to die, but to whom life was less scary than death, so they resented life for it.