John 14:16,17 - And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever; ¹⁷Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you. 

Verse 26 - But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.

John 15:26 - But when the Comforter is come, whom I will send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me:

John 16:7,8  - Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you.  ⁸And when he is come, he will reprove the world of sin, and of righteousness, and of judgment:

John 16:13-15 Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will show you things to come. ¹⁴He shall glorify me: for he shall receive of mine, and shall show it unto you. ¹⁵All things that the Father hath are mine: therefore said I, that he shall take of mine, and shall show it unto you. (emphasized)

Romans 8:15 - The Spirit (itself) beareth witness with our spirit, that we are the children of God:  (??) himself

Verse 26 - Likewise the Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit (itself) maketh intercession for us with groanings which cannot be uttered.  (??) himself 

What does the Holy Spirit do?

He comforts – Jn 14:26; 15:26

He is power from on high – Luke 24:49