I think Doom just wants it for the big 'd,' it's a branding thing.

This one at least shows why about every Doom figure comes with the book now: From 2021, Darkhold: Alpha #1, written by Steve Orlando, art by Cian Tormey, color art by Jesus Aburtov.

Deep within Abysmia, beneath the United States, Doctor Doom's robots and his herald Victorious, discover the one, true, original Darkhold: previously seen incarnations were "a copy of a copy," which was perhaps inadvertently a safety measure. Reading from the true Darkhold caused madness, as the Scarlet Witch well knows: she has a vision of the usual terrible future to come, and tries to head Victor off, despite their past history. Which, um, your guess is as good as mine: that might be from the Children's Crusade, but it might be implied they knew each other before Doom's face was wrecked. Still, Doom had already read the book, through the eyes of his Doombots, and now sought to prevent Chthon's rise for his own purposes. He reads a story from the book, for her to interpret: how five defenders had once driven Chthon into exile, at the cost of their sanity. Wanda thinks they need to form a new team, with five in those roles; Doom declares that wouldn't be necessary, as he had all five aspects within himself, and heads off to confront Chthon alone. (Victorious believed it was too dangerous, and tries to go in his stead; only for Victor to condescendingly remind her, who did she think she was talking to? Nothing was beyond Doom!)

Wanda has to summon a dreamer, a fool, a stoic, a hunter, and an artist: she gets Iron Man, Blade, Wasp, Spider-Man, and Black Bolt. Can you figure out who was what? While they're caught up on the stakes, Doom returns from Chthon's "other-world," which kind of looks like an alternate earth Chthon had already taken over. Victor looks like crap, like the remains of his face are leaking out of his mask; but while he thinks the heroes are doomed and leaves Victorious to aid them, he won't reveal anything else of what had happened, and immediately takes off "...to consider," and prepare. That really feels like Doom got his ass kicked but won't admit it.

The heroes are told, they have to read a bit from the Darkhold; just enough to "temper" themselves with madness. This fails miserably, and they mutate into new, red-themed outfits: evil Spidey points out "what about madness inspires self-restraint?" As the new Darkhold Defiled, could Chthon be stopped...? Evil Iron Man also appeared to be leaking flesh from his armor, which might make him the most striking of the bad heroes; each of whom would get their own Darkhold one-shot to be evil, or fight it off, either or. This would then wrap up in Darkhold: Omega, which appeared to be bringing back a long-forgotten, and probably previously misused, character. I think there's also a fairly big retcon here: that every appearance of the Darkhold prior, had just been a copy? But...that copy, it and at least some of the pages, had been just about indestructible themselves! That seems like it's giving Chthon a lot of juice, which may or may not be justified.