Akuryo Taisan was one of Rei's powers as a miko. It was also one of her first attacks as Sailor Mars in most versions of Sailor Moon. "Akuryo Taisan" is a Japanese phrase used to exorcise demons, which translates into "Evil Spirit, Begone."
In the anime, since Rei learned the chant as a miko and not as a Sailor Senshi, she could also use it while untransformed. She first used it on Usagi in episode 10, when she felt an evil spirit. She first used it as Sailor Mars in the subsequent episode to dispel Murid's poison and keep her arm from turning to stone.
To perform this attack, Rei called out, "Akuryo Taisan," then placed an ofuda on the enemy. Sometimes she would also chant the names of the kuji - "Rin, Pyou, Tou, Sha, Kai, Jin, Retsu, Zai, Zen!" (臨、兵、闘、者、皆、陣、列、在、前！; when combined into a sentence, it literally means "all warriors have been lined up in formation here") - while holding up the ofuda before performing the attack. Usually it was used to immobilize an enemy, giving the Senshi time to attack, but could also be used to purify people of an evil influence.
This attack appeared in many forms in the manga. When Rei first used it in Act 3, it looked similar to the anime in that she threw an ofuda at Usagi when she felt an evil presence. When she used the attack later after transforming into Sailor Mars, the attack did not seem to include the use of any ofuda, but rather appeared as a ball of fiery energy, similar to Youma Taisan. At that point she used the attack to surround Jadeite with flames which burned him to death. When she used Akuryo Taisan against Nephrite's shadow in Act 4, it looked like a wall of flame. This was the only attack Rei ever used during the Dark Kingdom arc. After that arc she used it only one more time in the main manga storyline: during the Dream arc in Act 36, she used Akuryo Taisan with a single ofuda in order to repel Tiger's Eye. She also used it against Zoisite in the manga side story "Casablanca Memory," where Sailor Mars performed the attack by using numerous ofuda. In the third Exam Battle story, when Rei was possessed by Ghost Sistern, Sailor Venus had to use this attack to destroy the spirit, leading Rei to become annoyed at her later.