Bio: White was the shadowy leader of the Threshold, who revealed himself only in the final story of the arc, "Wormwood".
Notes: Pinning down White's first appearance is a little tricky. It's assumed (but not confirmed) that he was "not seen" in the background from the very start of the arc. He could have been the figure that kidnapped Peri at the conclusion of "The Curse of the Scarab" in issue #230. The story which explains where Peri went, "Ground Zero" doesn't particularly make matters any clearer, as there's an unnamed Threshold agent in that story, too. While this could certainly be White as well, it could equally be Chastity, who has a big "reveal" moment of her own later in the Threshold Saga.
For these reasons, we'll set White's first appearance at the time his character is actually named and shown "out of the shadows".