Who are Baruch and Balthamos in the novel, The Amber Spyglass?

Baruch and Balthamos are the two angels who want to bring Will and his knife to Lord Asriel. Balthamos is possibly female, but only responds in the negative when asked if he/she is a man. However, the pronoun "he" is used for Balthamos. Balthamos does not approve of Will's actions but is powerless to stop Will from following his own course. He provides guidance to Will as Will travels. If there was a contest for Crabbiest Angel, Balthamos would win. Baruch is Balthamos' companion and a much younger angel who was a man in Will's world.