Seventh-Day Adventist Beliefs: God the Holy Spirit
God the eternal Spirit was active with the Father and the Son in Creation, incarnation, and redemption. He inspired the writers of Scripture. He filled Christ's life with power. He draws and convicts human beings; and those who respond He renews and transforms into the image of God. Sent by the Father and the Son to be always with His children, He extends spiritual gifts to the church, empowers it to bear witness to Christ, and in harmony with the Scriptures leads it into all truth.
--Fundamental Beliefs, 5
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I think a lot of people consider the Holy Spirit a female entity (insomuch as gender can be reasonably assigned to a deity). I don't know how well I agree with that, but it's plausible even if only because I know so very little about the Holy Spirit.
Usually the Holy Ghost is identified with the conscience. From this, the unpardonable sin ("the sin against the Spirit") is taken to mean, roughly, killing the conscience. This makes a kind of sense, because if you take away your desire to be pardoned, you won't ask for pardon, and very likely won't be pardoned. That's how I think of it; I'm sure there are other explanations.