Brine Vassal enemy bugged?

So I'm trying to do the "Storm on the Reef" prophecy, which requires you to kill a rare brine vassal.

I've been farming it for about 30 minutes now and have found 2 rare brine vassals, however once I get close to them they do a dive animation into the ground and never resurface, I've walked around the area for a few minutes but they never came back.

Here's a .gif of exactly what it looked like the second time: https://gfycat.com/ConfusedBlindChital

If this is not a bug can someone please explain how to make him resuface?



Also enemies trapped in essence that you defeat do not count (assuming they are the right mob), not sure if this is a bug or not however.

I second this, have got the same exact issue. It is RNG enough to even encounter the mob once every 20 runs but then not even fulfilling the prophecy =/ hope this gets fixed in the future.

The prophecy does not guarantee a unique from the first rare Brine Vassal that you come across. It might trigger from an Essence monster, it might not.