The fictional device that lets Desmond Miles relive genetic memories is called the Animus.
In Assassin’s Creed, the Animus is a machine developed by Abstergo Industries. It allows a user to access inherited memories encoded in DNA, presenting those memories as interactive experiences. Desmond uses it to experience the lives of ancestors such as Altaïr Ibn-LaʼAhad and Ezio Auditore.
The device gives the series a narrative link between modern-day science-fiction scenes and historical settings. It also explains why a modern character can appear in events that happened centuries earlier without literal time travel.
The Helix is a later Abstergo entertainment platform and is not the original machine used by Desmond. The Animus concept also drives the franchise’s recurring themes of memory, ancestry, surveillance, and control. Although the games depict the memories as playable worlds, the story presents them as reconstructed experiences based on genetic data.