Biomod aims to improve the game by adding new features and refining existing ones, while leaving the story and core elements intact. Biomod is an add-on to the popular Shifter mod, which must either be installed prior to Biomod, or be installed at the same time through the Biomod installer.
Biomod includes most of the features in Shifter, such as new weapons and Augmentations, in addition to several new ones. An autosave has been added, in addition to a physics-based ledge grabbing action similar to the one used in Deus Ex: Invisible War. Keyring Nanokeys and computer passwords can now be pickpocketed from living, conscious enemies. Augmentations have been further refined, and now only use up the player's Bioenergy in context as opposed to on activation (i.e. Microfibral Muscle only uses energy when an object is being lifted, and Aggressive Defense System only uses energy when a projectile is being destroyed). The Swimming skill, widely thought to be useless, has been replaced by the Athletics skill, which determines other factors, such as running and jumping ability, as well as swimming, making it much more useful. The Regeneration aug, widely thought to be overpowered, has been toned down, and now only repairs health when the player is far enough from enemies or is not hit by enemy fire for a substantial period of time.
The mod's author has removed the skill system from shifter, which awarded more points for a "stealth bonus" upon completing a mission appropriately. In the author's words, this skill system promoted a single play style, and made the game too easy, as many skill points could be accumulated over the game, making every skill affordable. Adequate skill points are still awarded for completing objectives or exploring new areas.