Nemesis integrates hierarchical systems (e.g., planetary systems in star clusters, circumstellar disks, or binaries in galactic environments) embedded within the AMUSE (ascl:1107.007) library. This flexible, multi-physics, multi-scale algorithm decouples tight subsystems from the global environment, integrates them in isolation, and then synchronizes the micro- and macroscales at regular intervals. This allows high parallelizability, accurate energy conservation compared to direct N-body only runs, and seamless inclusion of the galactic tidal field and stellar evolution. The Nemesis package provides example tests to provide a way to gauge whether modifications altered the physics in ways not wished for, but also to allow a user to being familiar with the algorithm.