According to rabbit folklore, General Woundwort is a cousin of his.
In the animated series of Watership Down, the Black Rabbit of Inlé makes a full appearance in the third season of the series, enraged by the fact that the still-living Woundwort threatens the world of the living and aims to build an empire of destruction in the Black Rabbit's name. He appears before Campion, who had miraculouly survived a cave-in between Watership Down and Efrafa, and chose him as his agent, tasking the rabbit to stop Woundwort from achieving his goal. Afterwards, The Black Rabbit of Inlé appears before Campion in visions during the season. His dark curse placed on Campion saves the rabbit from being found out by Silverweed in Darkhaven, who had the ability to look into the hearts of other rabbits to see into their mind.
In his final chat with Campion, the Black Rabbit of Inlé reveals that he will let Campion and his friends live, but reveals that the one who will summon the Black Rabbit to claim Woundwort and his army of Darkhaven rabbits will have to surrender to his dark embrace.In The Magic, Silverweed summons the Black Rabbit of Inlé using the magic he took from Hannah, despite knowing what will happen if he does. In a wind storm, the Black Rabbit appears before Woundwort and his army of Darkhaven rabbits atop Watership Down. Woundwort bows before the Black Rabbit and claimed that he and his army were there to do his bidding, but the Black Rabbit coldly replies that his empire is not of the world of the living, and that no creature uses his name for their own dark purposes. In a vicious whirlwind, the Black Rabbit of Inlé takes Woundwort and the Darkhaven rabbits to the Shadowlands and disappears without a trace. After the battle, Silverweed is revealed to be the one the Black Rabbit will take, when he has aged dramatically as a price for using the magic.
Despite being the darkness of rabbit folklore the Black Rabbit is shown to be assissting the rabbits of Watership Down and through Campion guiding them to defeat Woundwort.
The Black Rabbit has a dark, sinister and menacing voice and even General Woundwort bows in his presence. Despite being tasked with taking dead creatures to the Shadow Realm, the Black Rabbit does not want the Shadow Realm to be brought to Earth by Woundwort's madness, claiming that his empire is not for the world of the living, and no creature should use his name for their own dark purposes. Despite his reputation in rabbit folklore, the Black Rabbit does not seem to actually be evil as he spends the entire third series subtly helping the Watership Down rabbits, and Campion in particular whom he appears to in dreams or visions, in order to defeat Woundwort. Nonetheless he is unwilling to help them unless they give him something in return and therefore ages Silverweed to the point of near death when he uses the Magic to summon him.
Although he is only capable of physically appearing through the power of magic, the Black Rabbit has the ability to enter dreams and manipulate events from the Shadow Realm. His immense and terrifying power is shown in the final episode when he takes control of the wind, blows away Woundwort's entire army and takes them to the Shadow Realm.