Use a flying pet or ride the hot air balloon (which costs 5 Bucks) to reach the Sky Castle.

Located on the grey cement bridge leading toward the castle. Blue Crystal: Found near the campsite and the red bridge.

Touch the RB Battles Trophy at the peak to receive the badge and a limited-time pet wear item. Clarification on the "RB Bat"

To "Complete The Challenge," players had to locate and activate three hidden crystals (sometimes called totems) across the main map of Adoption Island:

Stand near each crystal until it glows, indicating it has been collected.

There is no specific "RB Bat" pet; however, the term likely stems from two popular topics often searched together:

Enter the castle, go to the upper floor, and use the trampolines/jump pads outside to reach the very top.