I don't think that "in the vast majority of video games like this that involve companions of variable moral stances and alignments, the games almost invariably introduce you to the good characters first" is even factually accurate. In Baldur's Gate, other than the companion that you start with because she's your sister, the first two companions you meet, on the first map, are both hella evil. In Tyranny, the first companion you meet is a bloodthirsty murder-bandit. In Kingmaker, the second companion you meet is literally one of the main villains of the game, and the third is a bloodthirsty berserker who despises the weak. In Dragon Age Origins, the first companion you meet besides the automatic mandatory Grey Warden is Morrigan, a witch who is decidedly not good. There's no "vast majority" here.
And this moral ambiguity is what makes them interesting. Well, beside being well written.
