Something that I always found interesting in this fandom is that many people interpreted the witnesses to be similar to the disciples of the Bishops.
But when you talk with Plimbo for the first time, he tells you this:
The way I understand this, is that the witnesses are creatures that come from beyond the island. The Bishops used to have control over the waterways and made sure that these beasts won't cross any lines, until the Lamb kills them of course.
After that, nothing stops the witnesses from entering the island, which is why they only appear after a Bishop dies. (not sure if them taking the Bishops place has any lore significance or if it's just for the game design)
I kind of have the headcanon that the witnesses are transformed/mutated mortals like the Bishops Disciples, but with the difference that they come from the mainland to stalk the waterways and the island. When they turn into the Lambs Followers, they barely have any memories of their old life left though.
In my old drawings and writing of the witnesses, I really liked having them trying to figure out where they are from and what their purpose was. Unless there is official lore they may never know though.
With this, I'm not trying to say that any other interpretations are wrong, because everyone can imagine those characters whatever way they want. I just kinda wanted to write about how I understood it from the game and what headcanon it gave me.
