Sentence:  O God the <WSD>"Holy Ghoſt</WSD>", Perfecter of the Elect, "Have Mercy on us." 
Meaning of the word marked with <WSD> tags:  The aspect (hypostasis) of the Trinity or Godhead corresponding to divine essence, which becomes present in and among the faithful (particularly inspired prophets) and is considered to proceed either  from God the Father alone or  from Him together with God the Son