Each element has its own habitat (five elements = five habitats) in which you can compete against other previously unknown pets of the element. If several pets of an element have already been unlocked, a specific pet can be selected beforehand by clicking on it to sent it into battle.

After selecting the pet you want to send into battle, tap the sword icon to start a habitat fight.
 
Pet habitat mobile

Each pet has different attributes, levels and character classes (warrior, mage, scout) and thus corresponding advantages or disadvantages against its opponent.

Rewards

When an enemy has been defeated, not only has the corresponding pet been explored, but you also receive XP, gold and pet food of the corresponding element as rewards. In addition, the egg of the explored pet will now be findable in quests if you meet its requirements.

Cooldown

You can perform a free habitat fight every 60 minutes. The waiting time can be skipped by paying a mushroom.