Slay Harbinger Aphotic.
When I sensed these... things... rising from below, I came to put them back down. I found the corpse of your friend and dragged him as far as I could before one of my fetlocks was broken. It is all that I can do to hold off these foul tendrils.
There is one that controls the tendrils and eyes. It calls itself Harbinger Aphotic -- I'm sure that you have heard it yelling from the south.
The harbinger stands out of range of my magic, but you could get to him. If you dare....