Figure Analysis
Abner is originally the chief general of Saul's son Ishbaal's army, fighting against David. But he defects from Ishbaal's side when Ishbaal takes issue with the fact that Abner is sleeping with one of Saul's former concubines. Abner thinks this is pretty ridiculous—he eloquently denounces Ishbaal (who gets scared) and switches sides. But after David celebrates Abner's somewhat traitorous switch, Joab kills Abner in revenge for killing his brother.
Abner isn't a particularly deep character. He plays his part of the plot, but he doesn't have any crazy speeches. But the fact that Ishbaal reacts negatively to Abner sleeping with one of Saul's concubines goes to show something interesting about how Israel viewed sex and kings. If you slept with one of the king's wives or concubines, you took some of his power, in a way, which becomes an even more important point, when Absalom sleeps with David's concubines.