The Holy Spirit
The Holy Spirit is God’s power, which He used to create all things, and continues to use to carry out His purpose (Genesis 1:2). The word “holy” means “separate” or in a way “special”. It is holy because it is 'of God' and used by him for specific activities – e.g. revelation of His thoughts, and the guidance of nations and individuals to achieve His purpose.
It is always His power, never man's - in the past believers possessed a portion of that power to heal and to teach at the direction of God. Believers were specifically given that power for a period, which was subsequently withdrawn at the death of the Apostles (Acts 8:14-18)
Though not shown in such visible miracles like healing today, this power of God can be seen guiding world events to accomplish His ends, outlined in the prophecies of His book the Bible.