A Doomed Pilgrim in the Ruins of the Future

I've been walking along a worn dirt path that meanders between the Gray Hills for three days, but it finally gave out. The slate-colored mounds extend for miles in every direction, covered with sharp, colorless bracken and peppered with fragments of old walls and buildings. The ruins are glossy black and obsidian.

I have vast and deadly patience and the summoning-name of a ghost burned into my memory.

There's an obsidian tower, the first two stories of which are still partly intact, atop one of the hills adjacent to the end of the path. I've just climbed it so I can get a good view of the land around me.
Something warns me of approaching danger. What warns me? Anyone should answer.