Mono Rail Scare

So I’ve been playing ds2 80+ hours now and I’ve had beached things over on the beach after the south distribution center appear and chase me before exploding and kindly leaving lots of Chiral crystals. But I was just travelling on the road at night just as I was getting to East Fort knot and a strange sounding cargo container was heading towards/above me it was lit red and I think 5 beached being also a bit red (I was worried they were mechs at first) were sprinting at me. I actually just drove into EFK (still unsure if they were mechs) and they actually exploded into chiral crystals at the top of the entrance to the building. Now I’m always checking the mono rail constantly. Has anyone come across them ANYWHERE ELSE along the mono rail?

Edit: apparently this will only occur at night