WARNING: The following contains spoilers for Thor #17, on sale now from Marvel Comics.
Thor has been in line for the Asgardian throne all of his life, preparing to succeed his father Odin as the All-Father's royal firstborn, but he has always had to contend with others vying to become Asgard's reigning regent. The vast majority of this courtly intrigue was fueled by Thor's adoptive brother Loki, leading to a super-powered feud that would eventually spill over to Earth and lead to the creation of the Avengers. And while Thor has since largely reconciled with Loki as he embraced his royal destiny and claimed the throne of Asgard, another family member has resurfaced and announces her own plans to forcibly replace Thor if he continues to be unworthy of the throne in her eyes: Angela.
Originally appearing in Spawn comic books, Angela made her transition to the Marvel Universe during the crossover event Age of Ultron as changes to the timeline transported her into the Marvel Universe. The subsequent crossover event Original Sin revealed that Angela had direct ties to the Marvel Universe all along since she was the secret, illegitimate daughter of Odin. Although she was born to the angels of the long-forgotten Tenth Realm Heven, she was effectively Thor's elder half-sister. After a war between Asgard and Heven, a vengeful Odin severed Heven from the Norse World Tree that connected the angelic realm to the rest of the Marvel Universe for eons. And while Angela has always kept her distance from Asgard's affairs, even after learning her true parentage, she comes back with a vengeance in Thor #17 by Donny Cates, Michele Bandini, Matthew Wilson and VC's Joe Sabino.
Angela and her stepmother Freyja summon a bickering Thor and Odin to a remote corner of the Nine Realms for an impromptu family reunion. While Freyja and Thor are happy to be reunited after some time away from each other, Angela is significantly more icy to her half-brother and father. Angela shares that she is well-aware of all the recent incidents that have happened in relatively rapid succession since Thor took the throne, from the arrival of the Black Winter to the recent revelation that Odin's enchantment on Mjolnir is weakened and unstable. Angela reveals that these incidents have graver ripple effects across the Marvel Universe and that, unless Thor does better, she will be forced to step in and take the throne of Asgard for the good of the kingdom and the wider universe.
Angela makes it clear that she has no desire or private ambition to succeed her brother and become Asgard's Queen, which is consistent with her character. Since entering the Marvel Universe, Angela spent time with the Guardians of the Galaxy and left Asgard behind when Odin informed her that she was his daughter to explore the other Realms. However, the has been happening around the Marvel Universe stemming from events in Asgard as certainly reached her attention and she and her understandably defiant brother Thor may soon have words as another interfamily squabble is born.
Thor has always had one of the more dysfunctional families in the Marvel Universe and, with Angela now angrily keeping an eye on him, Thor's biggest sibling feud doesn't appear to be with Loki anymore. Angela is one of the most formidable warriors in the Marvel Universe and is more than capable of giving the God of Thunder a run for his money on the battlefield. Thor may be the reigning All-Father of Asgard and the Nine Realms for now, but Thor has a challenger from inside his own family with Angela now looking over his shoulder.