Dark Souls Remastered | How to get Dark Orb (Sorcery), starting from Oolacile Township bonfire

From the Dark Souls wiki:

"Dark Orb is a Sorcery in Dark Souls. An abyssal sorcery uncovered by a sorcerer from Oolacile who was on the edge of madness. It launches a massive Dark Orb at the target, delivering a powerful, long-range dark attack. To cast a sorcery, you must use a Catalyst or Special Weapons that can cast Sorceries. "

You can read more about Dark Orb here:

https://darksouls.wiki.fextralife.com/Dark+Orb