In 4.5, Ghan-Buri-Ghan is no longer controllable, still summoned by the spell but you can't cast his abilities.
You can still see his previous roles and abilities below by expanding the page with the button below
Summon Ghan-Buri-Ghan, chief of the men of the Druadan Woods, along with three battalions of Druedain Archers to fight along side you on the battlefield for a short time. The archers have the passive ability of shooting poisonous arrows and of being cloaked when near trees.
Ghan-Buri-Ghan and his archers are best utilized to cover a retreat. Ghan's Reliable Guide ability is useful for speeding on your injured units to a faster escape, shifting the focus onto him and his archers. Ghan can also cloak injured units with his Secret Path ability, also allowing them to retreat. Finally, his Dastardly Poisoned Arrow is best used on an enemy hero or monster (any unit with a lot of health) as this allows the poison to achieve its maximum effect.