Complex sentence: These zombie like creatures are reanimated from the bodies of creatures slain by Others are will only die if totally dismembered or set aflame and it is not uncommon for the Night's Watch to find itself battling its fallen comrades only moments after their deaths.
Split into simpler sentences: These zombie like creatures are reanimated from the bodies of creatures slain by Others are will only die if totally dismembered or set aflame. Because of this, it is not uncommon for the Night's Watch to find itself battling its fallen comrades only moments after their deaths.