After siding with the Harpers (and them taking the latern) I went to Last Light Inn but managed to speak to Isobel as one of the first things I did which triggered a battle in which I failed to save her.
Then all the Harpers turned to Zombies and with Jahira we killed everything.. the lantern doesn't seem to be anywhere as far as I can tell.
I also had a mishap with Halsin when releasing him from cage so he's not available either which seems could have been an alternate route to dispelling the shadow?
I seem to be completely stuck.
Sodium doesnt react with water to form salt (aka sodium chloride), water only has oxygen and hydrogen which in the energetic reaction you see here gives you sodium hydroxide. Whilst not the worst thing around it isn't benign. The ecosystem of that pond could have done without it.
What happens when a pound of sodium is thrown into a river
interesting