I didn't play a lot of EA, so I missed a lot of changed storylines. However, from reading older posts, Astarion's backstory changed.
Apparently Astarion wasn't just a magistrate in Baldur's Gate 200 years ago. He was a corrupted magistrate who sold human/slaves to the vampires. He double crossed Cazador at some point and in retaliation, Cazador turned him into a spawn.
At some point, they changed his backstory to being saved from the Gur by Cazador (maybe to make him more likable than a slaver?), but they didn't change why he likes/doesn't like certain things. Like being mean, entertained by misfortune, or seeing anything wrong with owning slaves.
