I never got what exactly Vader is knighting Galen to
. Galen is not a Sith becoming a Sith. He can't while both Vader and Palpatine are alive, as both seem to firmly believe in and adhere to the Rule of Two, regardless of how often they take the letter of the law to the limits with all of these Dark Jedi disciples.
Is he making him his apprentice, then? But hasn't Galen been Vader's apprentice all his life?
Also, funny picture.