WARNING: The following contains spoilers for X-Men #20 by Jonathan Hickman, Francesco Mobili, Sunny Gho and VC's Clayton Cowles, on sale now.
In the current Krakoan era, mutantkind is faced with many possible futures. During her previous nine lives, Moira X, the longtime X-Men ally turned silent partner in the founding of Krakoa, has seen several of these potential outcomes, and she hopes to make her tenth life more successful for mutantkind than the others. And in her first appearance in many months, Moira reveals that she has a guide to the future through the diaries of the late precognitive X-Men villain Destiny.
At the end of X-Men #20, by Jonathan Hickman and Francesco Mobili, Professor X and Magneto enter Moira's No-Space. There, Moira is seen with Destiny's Diaries, which might contain the psychic mutant's most vital pieces of information and visions of the future. These diaries were introduced back in 1999's X-Men #94, by Terry Kavanagh and Alan Davis, and they were at the center of 2001's X-Treme X-Men series, by Chris Claremont and Salvador Larroca.
Destiny, as a mutant with precognitive powers, wrote these diaries from a young age. Destiny's Diaries contain all of her visions of the future, including possible futures which may not come to pass. It was always Destiny's struggle to decipher the true timeline, and then to reconcile that future with the most desirable outcome for mutantkind and for the whole world.
These diaries are fairly cryptic in their glimpses of the future, but they're still extremely important, for the sheer possibilities that they contain for mutantkind. One set of the diaries were gifted to Professor X, while the "X-Treme" X-Men attempted to hunt down the rest, wishing to keep them out of the wrong hands.
After "House of M," Destiny's Diaries were pursued by all sorts of mutant groups, including Exodus' Acolytes and Mister Sinister's Marauders, who all wanted information about the rebirth of the mutant race. In 2007's X-Men #203, by Mike Carey and Humberto Ramos, however, these diaries were seemingly destroyed in a battle between the X-Men and the Marauders.
Even so, Destiny's Diaries have returned, indicating that the books that were destroyed were either fakes or an incomplete set. Overall, Destiny's Diaries hold a major role in the future of mutantkind. The information in these diaries may be nearly indecipherable, but they still hold mutantkind's best chance of predicting how to thrive in a world that hates and fears them.
These possible outcomes are especially important to Moira X, who is determined to make sure that the failures from her past nine lives never come to pass in her tenth and final timeline. With Destiny's Diaries, Moira could feasibly decipher the future and shape it so that mutantkind finally prospers.
These diaries could explain Moira's general absence since the ending of 2019's Powers of X #6, by Jonathan Hickman, R.B. Silva and Pepe Larraz. Moira has probably been holed up in her No-Place trying to decipher Destiny's Diaries. This way, Moira could shape the world, and mutantkind, seizing her final opportunity to save her species.
One component of Moira's machinations could be related to Mystique. Raven Darkholme has been manipulated by leaders like Professor X and Magneto to do their bidding, with the promise of resurrecting her wife, Destiny. However, Moira has given explicit instructions to not resurrect her or anyone else who can see the future, and an enraged Mystique can see through their false promises. On some level, this could provoke Mystique to turn on Krakoa is part of Moira's plans, based on a future she read in Destiny's Diaries. It's unclear exactly what Moira's endgame could be, but manipulating Mystique seems to be part of her plans.
Of course, Destiny's Diaries could be negatively influencing Moira as well. When Mystique first met Destiny, for example, she went mad trying to shape the world based on Destiny's Diaries. This is exactly why the X-Men didn't want Professor X to possess the diaries to begin with. As Moira potentially obsesses over Destiny's Diaries, the results could be catastrophic for the future of the X-Men and mutantkind as a whole.