Walkthrough: At the end of Route 2 is Verdant Cavern, the location where your first Island Trial will take place. This is Captain Ilima's Trial that he created, one the sees you have to find Rattata hiding within rocks. Each time you find a Rattata, you will be forced to battle them. About halfway through the Trial, Team Skull will appear and battle you with their Level 11 Drowzee. After defeating them, you will be able to find the third and final hiding Pokemon, this time being a Raticate instead of a Rattata.
After defeating all three of the hiding Pokemon, you will be able to proceed to the Trial Site Area of Verdant Cavern. Here, you will battle the Totem Pokemon of this Trail, which just so happens to be another Raticate. This Raticate will be at Level 12, having its Defense Stat increased as the battle begins. During the battle, Raticate will call on other Rattata to come aid it. After defeating the Totem Pokemon and all of the Pokemon is calls upon for help, you will defeat the Trial and earn the Normalium Z-Crystal.