I Am Become Death
Sendoku isn’t Vishnu, but as a newly minted Death Knight, subject of the Lich King, he is a harbinger of death, one who uses terror like a madman’s cudgel and fear like a torturer’s scalpel.
Early in his career, he was told that the hunger gnawing at his soul could only be sated by killing. His very first fight set the tone for his existence, as he was told to fight a fellow initiate to the death. The later massacre of scores of soldiers was only a mild escalation in his ultimate task to eradicate all life on Azeroth under the direction of the Lich King.
He is not quite alive, having been reanimated to serve in thrall to the Lich King, nor is he truly dead or undead. He and his brethren are at least somewhat mortal, as some have not survived the Lich King’s war efforts. So he’s understandably confused about his existence, and the suggestion to focus on obedience to the will of the Lich King and the tasks at hand undoubtedly help efforts to ignore exisistential musing.