This page explains how to find the Rona Kachta shrine.
How to Find the Shrine
You might also want to get the Ancient armor set from the Akkala Ancient Tech Lab before you look for this shrine.
From Rin Oyaa Shrine near Hebra Tower, go southeast. Float down from the edge of the cliff to reach Tanagar Canyon. Go northeast in the canyon to find the Forgotten Temple.
The entrance to the temple is in the middle of the wall. Try to float down into the entrance, or climb up if you are at the bottom of the canyon.
There are many Decayed Guardians just inside of the Forgotten Temple. If you equip the Ancient armor set, you can survive even if they hit you. You can either try to carefully kill the Guardians using Perfect Guards (press A while shield is raised) or shoot them with arrows or hit them with weapons. Or you can just keep moving and floating on the updrafts so that their laser blasts miss you.
Keep going northwest through the Forgotten Temple to find the Rona Kachta Shrine. You can optionally pray at the big Goddess Statue behind the shrine if you want to exchange Spirit Orbs for Heart Containers or Stamina Wheel upgrades.
About the Shrine
The treasure chest in the shrine contains a Great Flameblade.