Dynamic Event bug, Bloodtide Coast
I had a similar problem. There ended up being a single risen krait that would fight one of the guards and end up dying. As the numbers of killed risen goes up, you should see an extra enemy accompany the krait until the end of the event :d
This all takes forever; so in order to speed things up, I went around to the weapon crates and killed the risen that appeared with the risen fish.
I’m guessing these are bugs, as this makes absolutely no sense xD
But at least it’s doable.