Hyzenthlay was an Efrafan doe and one of the representative leaders of a group who unsuccessfully tried to convince General Woundwort to allow herself and some other does to leave the warren due to overcrowding. When Bigwig infiltrated Efrafa, secretly planning to help some does escape, he befriends Hyzenthlay. She is described as sensible and strong and able to think on her own account.
Led by Bigwig, she is one of the rabbits who escapes along with Blackavar and other Efrafan does to live in the Watership Down Warren. After the escape, the Battle of Watership Down took place soon after they returned to Watership Down Warren. The Watership rabbits won the Battle against Efrafa.
In the film, it is said by Vervain, one the Efrafan captains that she is a disturber. It is also mentioned that the council ordered her to be strictly supervised by one of the captains.
Main article: Primrose
In the TV series, Hyzenthlay was replaced by another character called Primrose as Hazel's mate (or was at least renamed Primrose, thus giving another appearance). Her sixth sense is absent in this series, and she and Hazel eventually have kittens.
In this adaptation, she is far less trusting, and refuses to talk to Clover, who was captured and taken to Efrafa, denying that she is indeed Hyzenthlay out of worry that Clover is a spy. Later, Bigwig enters the warren, claiming to be in the same warren as Captain Holly, who'd also been there, along with Bluebell and Blackberry, only to be called a liar. She doesn't trust him until he says what Holly thinks of her. She is ordered by Captain Orchis, who holds a grudge against her for her role in his brother Vervain's death (who was ran over by a train in attempts to capture Holly, Bluebell, and Blackberry, whom she'd helped escape) to spy on the other rabbits who desire to escape, or she would be executed.
All of the does as led by Bigwig successfully dig a tunnel up to the surface and attempt to run away, but they are stopped by a group of Efrafan Owsla. Luckily for Bigwig, they believe that the does were trying to trick him, and thus, his cover is maintained.
After this, Hyzenthlay tells Orchis that she will spy for him if the other does have better conditions. However, Orchis ordered Hyzenthlay to be executed and said that he already has spies and that he was ordered by General Woundwort to get her to spy, so that he could break her, and laments on how easy it was. Hyzenthlay later learns that one of the other does Nettle had been the spy. Clover attempts to spare her by offering to be Woundwort's queen, but he tells her that he doesn't make deals, and Hyzenthlay's execution is not stopped. Orchis orders Bigwig to execute her, so that he can gain his trust, but he instead pummels the captain, and scares off the guards. The two of them gather the does and Blackavar, and escape. However, they are once again cornered by Efrafans, this time with Woundwort among them. Just as the mad general is about to strike, Kehaar swoops in, tackling the Efrafans, and allowing his friends to escape.Hyzenthlay is taken back to Watership Down Warren, and there, she becomes Holly's mate, but the Efrafans track them down. She, along with Thethuthinnang, makes the ceiling fall on Efrafan guards in battle. She eventually gets cornered by Efrafans, but Holly saves her and tackles them. Sadly, they overpower and kill him. She is devastated at the sight of her dead mate, and Blackberry has to push her back into the burrow. After the defeat of Woundwort at the hands of Bigwig and Bob, she lives out the remainder of her days at the warren without a mate.
She is described by Bigwig as being smart and sensible, but also strong, tough and able to think on her own account.