Baba Yaga is a female Tyrannosaurus Rex currently residing in Siberia. She was largely responsible for the deaths of soldiers and wildlife in the surrounding wilderness. She was also very tough, as she was able to resist three darts full of very strong tranquiliser for five minutes before the drugs felled her. She apparently didn't like competition, as she didn't hesitate to kill one of her own kind when he tried to eat her prey. After finishing off her opponent she disappeared into the forest and was last mentioned stalking a herd of Antotitans. It is unknown what happened to Baba Yaga afterwards, but she is most likely still at large. She is named after a Russian witch of the same name, because the dinosaur's legs reminded the Russians of the witch's house, which is said to walk on chicken legs.
She never appears in the book until the final chapters, though she is mentioned several times. At the start of the book, she ambushes and kills a lone soldier named Dima, who was smoking a cigarette. She later attacks a truck that was meant to collect Abby Maitland, Connor Temple and Nick Cutter as well as a number of Russian personnel, flipping it into the treeline and killing two of the occupants, though the third escapes. She stalks the group before provoking a stampede of Anatotitans. When the team searches for the anomaly, they encounter a wounded Torosaurus calf and while they are preoccupied with its agitated parent, Baba Yaga carries the calf away and eats it. She is briefly caught on camera by Sukhenkiy Yushenko before she kills him. She finally appears physically, when she attacks and eats Yuri Torosyan. When a soldier opens the door of his hut to investigate, she looks in and sniffs him. He promptly slams the door shut. Baba Yaga doesn't take kindly to this and bites right through the door, killing the soldier. When another shoots at her, she eats him as well. She then attempts to eat Abby Maitland, Grisha Bulov, Rina Suvova and Natacha Antila, though Abby distracts her by throwing a folding chair at her snout. This allows the latter three to escape, though the Tyrannosaurus chases after them and almost eats Bulov. Abby then shoots her twice with a tranquilizer gun, causing her to switch targets. She is shot a third time to no apparent effect and trashes the camp in her pursuit, crushing a 4x4 under her massive foot. Before she can eat Abby, Cutter comes to the rescue with an AK-74, though they are soon cornered by the massive hyperpredator. Just as she is about to eat them, the tranquilizer finally takes effect and she collapses headlong into the snow. Her next appearance is that of a climatic anti-hero, as she attacks a younger male Tyrannosaurus that was just about to eat Cutter, though this could also have been the result of a severe hangover from the tranquilizer. She emerges victorious and stomps off into the forest roaring in victory.