This is about the only thing that the whole community really doesn't have a full understanding of so I'm going to list what I know, what I've read, what my theories are and how to make a vagrant more likely to appear.
So we know for a fact there are four different vagrants with most people understanding that there are good and bad ones due to one pair being aggressive while the other pair runs away from the player and digs into the ground much like the crystal lizards (A rumour as I have never seen this type of vagrant when playing).
Since more info has surfaced over the years it appears that the bad vagrant is spawned by players losing humanity from their humanity counter permanently while the good vagrant is spawned by people dropping unwanted items (like black Knight weapons when farming chunks in the Kiln). With this in mind I think it could be an idea to start naming bad vagrants humanity vagrants and the good vagrants item vagrants as this gives a better understanding what these vagrants are all about.
If you find a random item on the floor that looks like it was dropped by you when you haven't, this is actually a drift item that has come from someone else's game. If you leave it long enough, die and reload the game enough times, these drift items will turn into item vagrants. So if you want an item vagrant to turn up in your game, make sure that when you come across a drift item that you don't pick it up and keep a reminder to go back later to see if the item vagrant has spawned.
Differences between spirit vagrants (red) and real world vagrants (white) is still mostly unknown, however I have a theory on them. We know that vagrants only appear when connected online so it isn't a case that the real world vagrants spawn in people's worlds if they are offline all the time. My theory is that the difference between them is how they spawn.
Real world vagrants spawn when a game has been loaded or reloaded.
Spirit vagrants spawn live in gameplay.
I also have a theory that these spirit vagrants drop better quality items, del more damage and are only available in NG+ and over, much like gravelord cursed only works on you when you are in NG+ and over.
Also we now know that you can have more than one vagrant spawn in your world at the same time even in close proximity.
If anyone knows any more information that has been missed out here or have any theories they would like to share please post them.
Also it could be worth updating the wiki on our better understanding of vagrants.
So we know for a fact there are four different vagrants with most people understanding that there are good and bad ones due to one pair being aggressive while the other pair runs away from the player and digs into the ground much like the crystal lizards (A rumour as I have never seen this type of vagrant when playing).
Since more info has surfaced over the years it appears that the bad vagrant is spawned by players losing humanity from their humanity counter permanently while the good vagrant is spawned by people dropping unwanted items (like black Knight weapons when farming chunks in the Kiln). With this in mind I think it could be an idea to start naming bad vagrants humanity vagrants and the good vagrants item vagrants as this gives a better understanding what these vagrants are all about.
If you find a random item on the floor that looks like it was dropped by you when you haven't, this is actually a drift item that has come from someone else's game. If you leave it long enough, die and reload the game enough times, these drift items will turn into item vagrants. So if you want an item vagrant to turn up in your game, make sure that when you come across a drift item that you don't pick it up and keep a reminder to go back later to see if the item vagrant has spawned.
Differences between spirit vagrants (red) and real world vagrants (white) is still mostly unknown, however I have a theory on them. We know that vagrants only appear when connected online so it isn't a case that the real world vagrants spawn in people's worlds if they are offline all the time. My theory is that the difference between them is how they spawn.
Real world vagrants spawn when a game has been loaded or reloaded.
Spirit vagrants spawn live in gameplay.
I also have a theory that these spirit vagrants drop better quality items, del more damage and are only available in NG+ and over, much like gravelord cursed only works on you when you are in NG+ and over.
Also we now know that you can have more than one vagrant spawn in your world at the same time even in close proximity.
If anyone knows any more information that has been missed out here or have any theories they would like to share please post them.
Also it could be worth updating the wiki on our better understanding of vagrants.