God's 'alien' works are these: to judge, to condemn, and to punish those who are impenitent and do not believe. God is compelled to resort to such 'alien' works and to call them His own because of our pride. By manifesting these works He aims to humble us that we might regard Him as our Lord and obey His will. (LW 13:135)
Although He is the God of life and salvation and this is His proper work, yet, in order to accomplish this, He kills and destroys. These works are alien to Him, but through them He accomplishes His proper work. For He kills our will that His may be established in us. He subdues the flesh and its lusts that the spirit and its desires may come to life. (LW 14:335)
Not a particularly nice take on God - judging, condemning, punishing, subduing. But, then, our idolatry and our addiction to that which is not life and not love is not nice. Luther insists that such works are "alien" to God because his "proper" and essential work is life and salvation. But, given our sinfulness, brokeness, and blindness, to work God's life and love into us, God must destroy that which is in us that quenches the Spirit and keeps its desires from coming to life. Perhaps alien to God, definitely unpleasant for us, such work appears necessary for our salvation.