From the Back Cover:
When these two villians pool their resources it's a serious matter...
In his past struggles with the JLA Matter Master used his Mentachem Wand to control and shape pure elements to his every whim.
When Dr. Alchemy tangled with the Flash he used his Philosopher's Stone to transmute elements.
Now, they are planning to combine the powers of both of their inventions to forge a more potent weapon.
And the villains plan to act upon their goal in Pittsburgh, the home of Firestorm the Nuclear Man!