(This post is based on a conversation I had with @midnight-in-town.)
As @glacierspirit has noticed, Violet is wearing an accessory on his outfit that looks very similar to Undertaker’s mourning lockets.
Assuming that these are mourning lockets as well, it raises the question to whom they refer to. It looks like there are six lockets, so has Violet already lost six dear people in his young life?
But, remember the Weston arc? The (former) P4 killed Derrick, his friends and vice-principal Agares. So in total they killed six people:
Could Violet’s lockets stand for these six people? That would mean that he’s mourning their deaths and therefore, regretting his actions.
That kinda contrasts to what we’ve seen of the former P4 in the current arc. Like Greenhill has told Edward, they seem to have found their happiness again. But as analyzed it this post by @erebuscheslock or here by @midnight-in-town, Violet doesn’t seem to be that enthusiastic about this cult as his fellow comrades and Bravat’s influence doesn’t work that good on him.
So maybe these lockets are a sign that Violet still regrets what happened at Weston.
This grave that Sebastian found at the end of the chapter is probably connected to what’s happening at the meetings of this sect. So it seems like the former P4 haven’t escaped from their past but have stepped yet into another situation that involves murder. Maybe Violet wants to help the others to escape it before it’s too late.