Recently, Pinnacle has been promoting a Kickstarter involving Stone and "The Cackler". Here's a quick snippet:
The third Deadlands Plot Point Campaign is on its way, featuring everyone’s favorite hero-killer, Stone! But we’re going to bump up the “dead factor” and combine him with the long-awaited tale of the Weird West’s oldest and most mysterious Harrowed—teased since the beginning of Deadlands in 1996—the Cackler!
I've heard of Stone (he's in the Marshal's section of the Player's Guide for one), but apparently the Cackler lives up to his epithet as "the most mysterious Harrowed" because I've never heard of him, despite having read a fair amount of Deadlands Classic and Deadlands Reloaded. (And references to him must have been really subtle if he was teased since 1996).
Since he's described in that writeup as "the oldest Harrowed", I presume that he's the one described in the entry for Stone in Deadlands Reloaded Marshal's Handbook.
Stone is the first Harrowed of the Reckoning. That's not to say he's the first Harrowed—that dubious distinction lies with some else (and we ain't sharing yet, partner).
However, it's not clear if that's the Cackler or not since oldest does not necessarily mean first (the first might have been killed off for good).
So who is the Cackler and what book or books has he been in before this upcoming graphic novel?