Blackavar is a rabbit with very dark fur from Efrafa. He tried to escape Efrafa when prevented from joining the Owsla only to be caught by Campion. As punishment, Blackavar's ears were ripped to shreds and he was kept in solitary confinement to discourage further escape attempts. He was later liberated by Bigwig, when he quickly proved himself an expert tracker and ranger, and Hazel came to trust and rely upon Blackavar.
Blackavar's mother was one of the rabbits taken prisoner when General Woundwort attacked the warren in Nutley Copse and his father was an Efrafan captain who had been killed on Wide Patrol. Blackavar, proud of his father, had grown up with the resolve to become an officer in the Owsla. But together with this there had came to him from his mother a certain resentment against Efrafa. He befriended some of the does who wanted to leave Efrafa and encouraged them to give Woundwort their proposal. When the does were separated to stop further plans to leave or escape, Blackavar tried his luck at running during his silflay. Getting as far as Campion, he gave the latter rabbit some trouble, but was brought back. The Council tore his ears and decided that he must be shown to all of the Marks and tell anyone who asks what happened to him that he is a traitor and the Council were merciful.
When Bigwig meets him, he decides not to leave without Blackavar, especially after Hyzenthlay tells him she is sure he will be killed after he is presented before every mark. Given a small warning ahead of time, Blackavar helps Bigwig fight off his guards and runs with he and the does. Hazel finds Blackavar to be a useful tracker and good fighter. After he left Efrafa to Watership Down with the does, he became very trustworthy and he soon became great friends with Holly and Silver.
In the film, Blackavar has his ears ripped to shreds by two Efrafans and is nearly beaten up to death by them, but he survives and is used an example to any others that would try to escape. In front of Bigwig, Blackavar is threatened by Vervain, and claims "the council were merciful to him" and the two leave him alone.
After Bigwig injures Chervil, Blackavar escapes with Hyzenthlay, Bigwig and many Efrafan does onto the river by boat. He makes it to the down with them, and says that he is willing to fight to the death so he doesn't have to return to Efrafa. When Woundwort breaks into the warren, Blackavar secretly stays behind while the other rabbits go further down into the tunnel. He bravely charges at Woundwort, but is instantly overpowered, thrown to the ground and brutally killed by having his throat torn out by Woundwort.
In the TV series, Blackavar is the only rabbit other than Primrose to escape Efrafa along with Bigwig, and his ears are whole. He has head fur like Bigwig's in the film, but it seems more like a hair piece and appears to be combed. Blackavar's last speaking appearance was in Escape From Efrafa, after which he appeared as a background character in The Vision, Prisoner of Efrafa and The Homecoming. He was also mentioned in the episode by Hazel, who told Dandelion to get Captain Holly, Blackavar and the rest. After that, he abruptly vanishes in Season 3 of the TV series.
In the miniseries, Blackavar is voiced by Henry Goodman.
He happens to cross paths with Captain Holly during an escape attempt and warns Holly of Efrafa. His ears are already damaged when he is first introduced. He is later captured and led around Efrafa as an example to all those who would try to escape. Bigwig is impressed by Blackavar's willingness to fight with all his might even while being wounded, and he helps Blackavar escape again with the does. While on the Down, Blackavar is shown to heal his wounds overtime before the final battle.
During the finale, Blackavar is recruited by Hazel in the mission to lead Bob to Watership Down, as Dandelion is injured during the battle and cannot run. During the chase, Blackavar trips and hurts his leg. However, before Bob can attack Blackavar, Hazel manages to distract the dog and lure him away from Blackavar, leading him to Watership Down.
- Blackavar survives the attack on Watership Down in the book, miniseries and possibly the TV series, but dies in the film adaption.
- Since the moment Blackavar is killed, Woundwort has his lips covered with blood for the rest of the film.
- In the TV series, Blackavar bares a resemblance to his voice actor, Stephen Gately.
- Blackavar is greatly respected by Hazel and Bigwig.