Opal

A new drug distributed commonly in liquid form. This is supposedly “the new crack,” as it is cheaper to distribute and more widely available. According to many underground news sources, this drug’s main distribution source is America itself. Opal is said to be a religious experience for many people.

This post, from lovemonger of Another Version of the Truth, implies that Opal induces visions of The Presence:

Opal puts you in touch with it. I’ve been on the spike for the past four years. I
stole money from my grandma, got caught, did it again anyway, just to cop. For
the last couple months, it’s been too hard so I went to Opal.

I saw the Presence yesterday. At first I knew it was the drug, just gripping me,
you know? And I laughed. Then the Presence turned around, like it was
LOOKING for me. 

Parallels have been drawn to Black Oil from The X-Files television series. (Someone with more knowledge about this should update.)

References

opalescenthaze.com -- Popped up on Feb 14, 2007. This site name is referenced in Consolidated Mail Systems, and is said to be an underground website for Opal users. However it has been proven to be FAKE.