The Nexia are a group of humanoid creatures that have the ability to use their cells to shift their body into different forms. They're able to re-arrange their entire genome structure to something as simple as a weapon, or something as great as another living being. In other words, their kind of like weaponized shapeshifters, granted their ability isn't portrayed as transformation, but as bodily modification. The Nexia do have limits though; using their abilities too much can cause a rejection of cells, and cause them to forcibly revert to their original form. Sometimes, it's even possible for their cells to divide rapidly in the wrong way, which causes their body parts to become deformed. Even though they can technically transform into other beings, they do not obtain abilities that is not biologically attached to the creature.[1]

  1. For instance, Draconians are able to sucessfully use magic due to them being born in tune with the Arcane Webbing. If someone were to forcibly become that race, magic wouldn't be an option as a method of attacks.