Warning: this article contains spoilers for The Darkhold: Omega!
Wanda Maximoff has just gotten the ultimate magical power-up, making the Scarlet Witch more powerful than ever before. Whether Scarlet Witch is considered a mutant or not, Wanda Maximoff has long been considered one of the most powerful beings in the entire Marvel Universe. She has the ability to rewrite reality itself, a power she once used to bring the mutant race to the brink of extinction; more recently, she wove an innovative spell that extended the X-Men's Resurrection Protocols, rewriting the future of the mutant race.
Scarlet Witch's greatest power is the ability to wield Chaos Magic, sorcery so rare Doctor Strange initially believed it was just a myth. This primordial magic was wielded by the Elder God Chthon when he ruled the Earth, and Wanda's ability to use it has tied her irrevocably to the demonic being, who is eager to return to this plane of existence. In Marvel's recent Darkhold saga, Scarlet Witch obtained a forbidden book of magic also crafted by Chthon, the Darkhold - another avenue by which he continually attempts to invade Earth. In The Darkhold: Omega, by Steve Orlando and Cian Tormey, Scarlet Witch turns its power against its creator.
Scarlet Witch realizes Chthon has placed too much of his power within the Darkhold, and she turns it against him - recognizing that to control the Darkhold is to control Chthon. But Wanda Maximoff does not only seek to control Chthon; rather, she wishes to restrain him, and she achieves this by absorbing all the power of the Darkhold within herself. "Now I am the true Darkhold," Scarlet Witch declares boldly. "You haunted me for so long. But in the end... you do not possess me, Chthon. I possess you." All the power of Chthon and the Darkhold now belong to Wanda Maximoff.
It's impossible to overstate how powerful Scarlet Witch has now become. Chthon was one of the first mystical beings, and the Darkhold is perhaps the greatest repository of magic in the Marvel Universe. The spells contained within the Darkhold created vampires and possibly werewolves as well, and they can bind the dimensions together in cosmic events of unimaginable scale. Demons and hell-hounds have been summoned and controlled through the Darkhold, and now presumably Scarlet Witch possesses the power to do the same. When the sorcerer Modred the Mystic was bound to the Darkhold, he claimed to wield all its power, and his party trick was an elemental storm of phenomenal power.
Scarlet Witch has always been considered one of Marvel's most powerful heroes. Now, though, she wields the power of an Elder God - meaning she dwarfs any other being on this dimension in power, including the Sorcerer Supreme. It's worth noting, of course, that Wanda Maximoff's power has often come with significant mental instability; hopefully Scarlet Witch can handle her ultimate power-up.