Zachariah was a high ranking angel and the direct superior of Castiel and a direct subordinate of the archangels, but after the fall of Lucifer and Gabriel fleeing, he served Michael and Raphael. He had been alive for over 6 millennia. He came to Earth following Uriel's death and after his betrayal was revealed.
He introduced himself to Dean Winchester as being the direct superior of Castiel. Like many of his angelic siblings, he supported the release of Lucifer so that Michael could kill him and Earth could be made into a paradise. After Lucifer was freed, Zachariah was then given the task to force Dean to give Michael his consent to use his body. His failure to get Dean's consent caused his angelic siblings to ridicule him and made him despise the Winchester brothers. He was finally killed by Dean in his last attempt to get Dean's permission.
Powers and Stats
Age: Millions, if not Billions of Years Old
Classification: Angel, Seraph
Powers and Abilities: Superhuman Physical Characteristics, Matter Manipulation (Cellular level), Energy Manipulation, Telekinesis, Pyrokinesis, Photokinesis, Smiting, Astral Projection / Dream Walking, Immortality (Types 1 and 3), Regeneration (Mid-High), Invisibility, Telepathy, Teleportation, Healing / Resurrection, Soul Manipulation, Time Travel / Chronokinesis, Immune to Time Stopping, Immune to Soul Manipulation as he doesn't have one, Mind Manipulation, limited Reality Warping, Power Removal, Time Paradox Immunity (Angels are immune to the effects of rewrites in the timelines)
Speed: Subsonic+ movement speed, with Massively Hypersonic reactions (Castiel is capable of Searching an Entire Town in seconds through Teleportation)
Lifting Strength: Class 5
Striking Strength: Small Building Class
Durability: Likely City level
Range: Town level for most abilities, Universal for Teleportation
Standard Equipment: Angel Blade
Intelligence: Superhumanly Intelligent (As an angel, Zachariah possesses a superhuman level of intelligence, both due to his age and nature.)
Weaknesses: Angel Blades, Enochian Sigils, and Holy Fire