Angels-HOLY SPIRIT (HOLY GHOST)

The Christian mainstream, both Protestant and Catholic, has traditionally
adhered to the notion of the Trinity, the idea that the one
God manifests in three “modalities,” the Father, Son, and Holy Spirit
(or Holy Ghost). The Holy Spirit, as an aspect of the godhead, is not
an angel—a creation of God—but is rather a direct expression of
God. Although this is quite clear theoretically, in practical expression
the Spirit manifests in ways that one might otherwise associate
with angels.
In the Gospels, for example, Jesus tells his disciples not to worry
about what to say when delivered up for trial. Rather, he asserts, they
should “say whatever is given you in that hour, for it is not you who
speak, but the Holy Spirit” (Mark 13:11). This kind of spiritual aid, in
which someone is spontaneously given the right words to say, is a type
of inspiration often attributed to angels. There are also many passages
in the Acts of the Apostles in which the Holy Spirit speaks to or otherwise
acts upon the early Christians in angel-like ways, for example,
chapter 13, verse 2:
While they were worshiping the Lord and fasting, the Holy
Spirit said, “set apart for me Barnabas and Saul for the work
to which I have called them.”
Here, if “an angel appeared before them and said” were substituted
for “the Holy Spirit said,” the passage would not seem in any way odd
or unorthodox.
In addition, the Commentary on the Apocalypse of the Blessed John
indicates that “by the angel flying through the midst of heaven is signified
the Holy Spirit.”