Zygarde Core is the individual that starts it all in the Zygarde line. It's form depends of the percentage of said Zygarde Cores and Zygarde Cells. The main difference in between the two, is that Zygarde Core are the fully conscious ones that make the pokemon truly function, meanwhile Zygarde Cells are their non-conscious minions that are around the world.

Zygarde Cores remain in watch in the region if any ecosystem crisis occurs. Even with their own will, most of the times they hide themselves on caves. The Zygarde Cells are used by the Cores to observe the ecosystem, and will reunite with the Core once it's needed for stronger forms. The Zygarde Core can order Zygarde Cells, commanding them to fly towards it to form Zygarde's body in order to protect the ecosystem. The Cores for sustaining themselves can absorbe sunglight, and can speak telepathically towards other Cores. 

This form alone doesn't have the power to battle, only being able to fight if reunited with other cells to transform to a higher form. However, in desperate situations, it can gather the energy of the land and/or fly towards other Cells for support. The ability "Core's Call" makes this possible.

Forms

The only way it can get certain forms is by collecting Zygarde Cells. 

Base Stats

HP: 30
Attack: 15
Defense: 10
Sp. Atk: 15
Sp. Def: 10
Speed: 25

Total: 105

Type Effectiveness

Damaged normally by (x1): STEEL, BUG, NORMAL, PSYCHIC, ROCK, DARK, GROUND, POISON, FLYING
Weak to (2x): DRAGON, FAIRY, ICE, FIGHTING
Immune to (0x): GHOST
Resistant to (½×):  WATER, ELECTRIC, FIRE, GRASS

LVL1: Thousand Arrows (Ground, Physical) / Power: 90 / Accuracy: 100% / PP: 10

LVL1: Thousand Waves (Ground, Physical) / Power: 90 / Accuracy: 100% / PP: 10

LVL1: Core Enforcer (Ground, Special) / Power: 100 / Accuracy: 100% / PP: 10

LVL1: Bind (Normal, Physical) / Power: 15 / Accuracy: 185% / PP: 20

It cannot learn other moves without acquiring the 10% form or higher. Its signature moves aren't as strong as what could have been with the other forms because of its lack of cells.

Normal & Shiny