I finally got around to do the Dark Chasm stuff. I've cleared the 3 mini-dungeons and lit the 3 braziers. Dark Lurker didn't trigger. What am I doing wrong? It also didn't trigger the covenant level-ups, aside from the first one.

You need to light the candles in the Dark Chasms. After that, you need to complete one Dark Chasm and he should appear.

You missed lighting one of the 3 braziers then. If you lit one, and then died, it doesn't count.

That could be it. I guess that's what must have happend with the one under Drangleic Castle. The other two I beat on the first try.

Try torch and then praise the sun!