Pets are a new way to increase your damage output towards the enemies. When you add a pet to your loadout, it will follow your hero in the battles, automatically attacking your common foes.
You can unlock pets through the Pet Summon in the shop. The summon requires either gems, or a Pet Summon Key. You can receive Pet Summon Keys from the Weekend Pet Rescue event.
All the pets have different abilities available for them from their skill trees. The first special ability is unlocked when your pet receives their first star.
The pet skills only affect the bullets shot by the pet - they do not affect any bullets shot by your hero!