In the Fox sci-fi drama, the sinister scientist, played by John Noble, is hoping to build the doomsday device to destroy our world and save his own reality.
"There is an enormous focus on how [the machine] can be activated and what it takes to do that," Abrams told TV Guide. "[We focus on] how it can be finished, and if it is, what are the implications."
Series star Jasika Nicole (Astrid Farnsworth) added that the choice between worlds is "going to rest on [the] shoulders" of Walternate's son Peter (Joshua Jackson).
"Peter is the only person who can power that machine," she explained. "That's really integral into which universe is going to survive."
Nicole and her co-star Lance Reddick previously revealed that the war between the two universes will escalate as the third season continues.
Fringe returns to Fox on January 21 at 9/8c.