Another possibility is that the antagonists are a part of a secret organization. They might be operating in Siberia for some hidden purpose and see Tony as a threat or a valuable asset. Their actions against Tony could be part of a larger, more complex plan, and Natasha has to figure out their motives and stop them while rescuing Tony.
There might be a new villain or a previously known enemy who has set a trap for Tony in Siberia. This antagonist could be a powerful figure with their own motives, like wanting to take over Stark Industries or gain access to Tony's Iron Man suits. Natasha would then have to face this antagonist to save Tony. They could have their own army or special powers that make the rescue mission more difficult for Natasha.
One possible plot point could be Natasha's stealthy approach to the Siberian location where Tony is in trouble. Maybe she has to evade guards or overcome various obstacles to reach him in time.
Maybe he uses his magic. Loki is a powerful sorcerer. He could have created a portal or used some sort of teleportation spell to get to Siberia quickly.
I haven't actually read this specific fanfiction, so I can't summarize it directly. But generally, it might involve Peter using his powers, like his spider - sense and agility, to rescue Tony who could be in some sort of danger in Siberia. Maybe there are battles against villains or difficult situations that Peter has to overcome to save Tony.
Well, without having read the 'peter saves tony from siberia fanfiction', I can only guess. It could start with Peter finding out that Tony is in trouble in Siberia. He then embarks on a journey there. Once he arrives, he might face challenges like harsh weather conditions in Siberia and also potential threats from enemies. Peter would likely use his wits and powers to get to Tony and save him. For example, he could swing through the icy landscapes or use his strength to break through barriers to reach Tony.
There could be a local Siberian healer who becomes an important figure in Tony's life, helping him with his pregnancy.
It could be a local Siberian warlord who sees Tony as a threat to his power. Maybe Tony's presence in Siberia disrupts the warlord's plans for the region, so he decides to eliminate him.
Peter might become more confident in his abilities. Saving Tony from Siberia is no easy feat, and successfully doing so could boost his self - assurance as a hero.
It could be some dark magic users from Lucy's world who see her as a threat. They might be trying to stop her from using her magic for good.
Maybe some of Tony's business rivals who have access to advanced technology. They could be jealous of Tony's relationship with Ultron and try to harm him. They might hire mercenaries or develop their own weapons to go after Tony. In this fanfiction, these rivals would be the main antagonists as they constantly try to break through Ultron's protection of Tony.
It could be a new villain that we haven't seen in the original Marvel universe. This villain might be able to manipulate Natasha's emotions and loyalty, making her betray Tony. For example, a powerful sorcerer who uses dark magic to control her.