Going into a little more detail with pup biology, all pups contain a core that is like a second heart that pumps their respective elemental attribute through them. These cores are located in their chest and can be revealed at will, though pups tend to be cautious about this.

If a pup's core is broken or destroyed it also means the end of the pup. However, should the elemental energy for the core be depleted, the pup will undergo regression and return to an egg state until it can regain elemental strength by either absorbing their current element or absorbing a new element and reform as a different type of pup.

The cores glow the respective color of their attribute and are made of multiple pieces that spin and rotate around one another.

From top to bottom and left to right the cores are:
Water, Earth, Fire, Wind
Time, Poison, Energy, Ice
Dark, Light