Illusion (Japanese: ) is a skill used by Rika in Phantasy Star IV: The End of the Millennium. It reduces all affected enemies' agility stat by an amount equal to Rika's agility stat. Rika's agility stat, each enemy's mental stat, and each enemy's psi sensitivity affect Illusion's success rate. Enemies immune to psi effects, particularly Machines, Saber Warriors, Ghosts, and most bosses, are immune to Illusion.
Illusion can be combined with Alys's Death skill in any order to do a Lethal Image combo.
Rika already knows Illusion when she joins the party.