
The solo mode is confusing for me too ╥﹏╥ How I understood it was that they were challengers once, but gave up their freedom to seek power ; and now they're anchored in the tower and can't go out ? But then does it mean they exist in each solo mode, so if Taehan kills them it won't change the other solo modes ? Or is it the same tower for these characters, it's just the challengers that are ?
And if I remember well the Guide of Sin are just monopolizing ressources to go further in the Tower ; that way they pressure every newcomer to join them (or die). They function on a hierarchy based on the floor you're in : the 20s, 30s, 40s, etc. The higher ups are the most influential and powerful (they're the ones we see talking in the round table in this chapter 109)
Sorry if my response isn't accurate it's been a while I've been reading this

So what I understand from the guides of sin is similar to @tea dealer, basically they want to monopolize resources and are scared of losing their lives by risking climbing further in the tower and want to cling on to the power that they have. To ensure they remain in power, they don't want to have to deal with other challengers becoming too strong and opposing them, so they try to get rid of them if they won't join their cause.
As for solo mode, I think of it as almost parallel universes, each player is in their own "universe" of the tower. The NPCs exist in all of these towers, but I'm not sure if Taesan's NPCs will have awareness of others in solo mode. Iirc though, they're all immortal after having signed contracts in the tower, so while they are bound to the tower & the god they follow, I don't think they can be killed by any of the players climbing the tower. Hope that makes sense!

Yes they do exsist for the other players. They started as players climbing the tower but gave up reaching the top and made a contract with the tower to achieve something else like revenge, finding their god, study magic etc and are now part of the tower and cannot leave it. So every player has them in their tower.
Can someone explain the Guide of Sin to me and how they work? I'm just so confused. They stop ppl from climbing bc why?
I also don't understand how solo mode works. So all these "NPCs" like the ghost, dwarf Smith, the witch that's learning magic, the Guide of Sin captains etc, are also available in the other solo mode player's tower? Bc they have to be since the other two met that one knight that followed the goddess of beauty(?) earlier in the story.