Ansem appears in Kingdom Hearts as the primary antagonist, initially lacking a physical body. He manipulates Maleficent into gathering the Princesses of Heart to serve his purposes. Once Maleficent has fulfilled her role, Ansem possesses Riku to regain a tangible form and confront Sora at the End of the World. Although he achieves his goal of reaching Kingdom Hearts, the light behind the door destroys him, restoring many of the destroyed worlds and putting others into a state of sleep.
In Kingdom Hearts: Chain of Memories, it is revealed that Ansem still exists and attempts to take over Riku again within Castle Oblivion. However, Riku manages to subdue Ansem and eventually uses the villain's power before purging Xehanort's Heartless essence from himself before battling Xemnas.
Ansem reappears as one of the main antagonists in Kingdom Hearts 3D: Dream Drop Distance, brought forward in time by Young Xehanort. He exploits the Sleeping Worlds to try to reopen Riku's heart to darkness. After being defeated by Riku in the Sleeping World version of the World That Never Was, Ansem later appears in Organization attire and attacks Riku and Mickey to prevent them from interfering with Xehanort's plan to convert Sora. It is revealed that Xehanort's scheme included Ansem using his bodiless form to contact Young Xehanort and enact a backup plan.
Ansem is voiced by Akio Ōtsuka in the Japanese version of the series. In the English version, Billy Zane originally voiced the character in Kingdom Hearts, but Richard Epcar has taken over the role in all subsequent releases and remakes.
