It's going to have to be a quest. Everything is quests!
I would say that it's probably better to go into your storyline, into your "quests_reaction.c". Then you can do whatever you like with it, without having to be concerned how it ties in with any other sidequests, or for that matter any other storylines. (For example, you do not want to put a sidequest involving Barbossa into the general "quests_side.c", otherwise someone could trigger it while playing the "Jack Sparrow" storyline, in which Barbossa already has a major part.)
Within your own storyline, the only difference between a main story quest and a side quest is that the main story does not depend on the side quest finishing. And that is controlled by how you trigger quest cases.
I'm not sure what you mean by "normal dialog file". All dialog files work the same way - a "dialog.h" file which contains the text the character will say, as well as your answers to that character; and a "dialog.c" file which controls how parts of the "dialog.h" file are used. The "dialog.c" file may contain an AddDialogExitQuest line, which triggers a quest case - your starter quest NPC will need one of these so that when you talk to him, a quest will start.
I would say that it's probably better to go into your storyline, into your "quests_reaction.c". Then you can do whatever you like with it, without having to be concerned how it ties in with any other sidequests, or for that matter any other storylines. (For example, you do not want to put a sidequest involving Barbossa into the general "quests_side.c", otherwise someone could trigger it while playing the "Jack Sparrow" storyline, in which Barbossa already has a major part.)
Within your own storyline, the only difference between a main story quest and a side quest is that the main story does not depend on the side quest finishing. And that is controlled by how you trigger quest cases.
I'm not sure what you mean by "normal dialog file". All dialog files work the same way - a "dialog.h" file which contains the text the character will say, as well as your answers to that character; and a "dialog.c" file which controls how parts of the "dialog.h" file are used. The "dialog.c" file may contain an AddDialogExitQuest line, which triggers a quest case - your starter quest NPC will need one of these so that when you talk to him, a quest will start.