“And so it is,” his second agrees. “The last combined Forerunner fleet made a stand out beyond Jad Sappar. Thousands of star roads sheltered and magnified the enemy’s strength, protecting swarms of ships—Forerunner ships—crewed by our own infected warriors. A perversion beyond imagining, but not beyond reality.”

“I do not need to imagine.”

“They will need us. Both of us … together.”

“And the Ark?”

“It’s our last defense. All that remains of the Forerunners.”

The two Didacts look up and out at the great swath of dusty darkness that is the nebula’s outstretched arm. The new-fired young suns within this black cloud are buried deep and do not yet shine through, though in thousands of years they certainly will.

“What else do you see?” the IsoDidact asks.

“What I’ve always seen, what we’ve always seen,” the Ur-Didact answers. “But now it’s different.”

There is something about this one that makes even Catalog uneasy, a coiled potential only partly visible in his duplicate.

“The light is over a hundred years old,” the IsoDidact says. “What could change?”

“Something deeper than frequency. Look again,” the Ur-Didact says. “The way it invades our eyes. Piercing. Slicing. Concealing. The light shuns us, space itself wishes to expel us. Can’t you see? We are no longer welcome here.”

This opening is not fortuitous. There is a slow calculation between the two.

“The Flood changes everything. Not just flesh. Space itself is infected,” the Ur-Didact continues. “That’s the power the Precursors once had … isn’t it? They shaped and moved galaxies! They created us! How did we ever manage to defeat them?”

“Perhaps they were powerful but naive,” the IsoDidact says. “But they’ve had ten million years to contemplate those mistakes.”

“Yes … The Graveminds suck experience from all sentient history. One of them did everything but absorb me. Saw right through me, understood every strategy I’ve ever devised. They’ve advanced far beyond the Primordial. In absence of old strategies, new ones must be made.”

“I don’t believe so,” the IsoDidact says. “What we saw years ago at Charum Hakkor—before you imprinted me—the result of a unique Halo test. Complete destruction of all Precursor artifacts. Back then, it seemed an awful aberration … But now we know what Halos are really capable of. They can destroy any structure that relies on neural physics. They are our last hope.”

The Ur-Didact turns aside, fists clenching. “And loose damnation on the stars?” he shouts. The IsoDidact is silent. The sky above is no less grim than these walls. “My wife sympathizes with our enemies,” the Ur-Didact says. “This quest to fulfill the Mantle has haunted me my entire life. And for countless millennia, we have failed to realize the one truth that could have saved us from the beginning. The Mantle isn’t to be inherited by the noble, it is to be taken by the strong.”