Archades is the Riddoranna Cataract on the future.

I told you the plains near Archades are submerged on the future.And Archades seems to be on the top of a mountain.A river comes from this mountain splitting in two as seen on the map.A bridge on Archades go accross the river.
Maybe the mist caused an overflow of the river(It seems to have the power to grow the monsters size so maybe it do with substances too).
If you still donīt believe consider the many similarities between the Hell Wyrm and Yazmat.
Now,the identity of the pharos on the past is your homework.