WARNING: The following article contains major spoilers for Batman #73 by Tom King, Mikel Janín, Jordie Bellaire and Clayton Cowles, on sale now.
The name of Ra's al Ghul is almost synonymous with that of the Lazarus Pit. The Lazarus Pits, of course, are the hidden life-restoring pools of rejuvenating chemicals that have allowed Batman's oldest enemy to live on for centuries. Tom King and Mikel Janín's Batman #73, however, puts Thomas Wayne -- Flashpoint's Batman -- on the hunt for something even more elusive, and potentially more powerful.
Thomas is searching for something called the "Nain Pit." With the body of his murdered wife Martha in tow, Thomas is looking for the means to bring her back to life. If that's so, why not simply locate one of Ra's al Ghul's Lazarus Pits and place her there? That question posits the notion that this Nain Pit has some kind of restorative property that not even the Lazarus Pits possess. What might this new, unheard of entity be capable of, and why has no one heard of it?
What's Wrong with a Plain Old Lazarus Pit?
Bruce Wayne, who's also been brought along by Thomas, deduces that his alternate-reality father is looking for something more powerful than a Lazarus Pit to resurrect his mother. But even the World's Greatest Detective admits that he's only heard rumors of such a thing. It stands to reason that Thomas would also know of the Nain Pit only through whispers, as well. And, by extension, he can only surmise that the Nain Pit might do what a Lazarus Pit cannot.
As miraculous as the Lazarus Pits are, they're not without their limitations. For one, they historically have been able to be used only once, so Thomas might simply not be aware of where to find a pristine and unused Lazarus Pit. They've also typically required that the subject immersed in them be alive, or at worst only recently dead. There's also that nasty problem of those emerging from a Lazarus Pit frequently going insane.
Where a Lazarus Pit Might Fail, a Nain Pit Might Succeed
Martha, of course, has been dead for decades. So, in all likelihood, not even a dip in a Lazarus Pit would be able to restore her to life in the way Thomas intends. And even if she were, a decidedly insane Martha probably wouldn't be the same wife and mother that Thomas wants to resurrect. And even if that were acceptable to him, there's the matter of simply finding a functioning Lazarus Pit that he could utilize.
There is precedent for Martha's body being placed in a Lazarus Pit not working out so well. In 2000's JLA arc "Tower of Babel" by Mark Waid and Howard Porter, Ra's al Ghul himself threatened to immerse the corpses of both Martha and Thomas. His intent, though, wasn't to revive them -- it was to reanimate them as mindless zombies. Flashpoint Thomas might very well be aware of this, and is therefore avoiding the Lazarus Pits for that very reason.
The Nain Pit, therefore, can be inferred to have greater restorative properties, with the ability to restore a long-dead Martha to true life, not as a zombie, and without the debilitating emotional and mental side effects. Or so he believes, at least. Since the Nain Pit is a new and unknown concept, to readers anyway, its actual capabilities remain a mystery and are open to speculation.
The Biblical Origins of the Pits
The Lazarus Pits were named, presumably, based on the last of three biblical miracles of resurrection performed by Christ, as told in the Book of John, when Jesus brought Lazarus of Bethany back to life. Interestingly, the Nain Pit also evokes references to The Holy Bible. Christ's first such miracle, as told in the Book of Luke, was also a resurrection, performed on a man from the city of Nain.
The Nain Pit, therefore, was likely named after Christ's first miracle resurrection, while the Lazarus Pit was named after the third. Does this perhaps imply a different, and maybe greater, power held within the Nain Pit? Is the Lazarus Pit potentially the "weakest" of such restorative pools in existence, implying that the Nain Pit might be the strongest? Does the Nain Pit hold the potential for all sorts of pending resurrections within the DC Universe?
There's no way to know until it's tested on Martha -- or someone else -- first.
For those wondering, Christ's second miracle resurrection was performed on a girl named Jairus, according to the Book of Mark. So, there stands to be a "Jairus Pit" sometime in the DCU's future.