You'll wake up on the beach - go left to discover your first myth stone. Turn around and start running down the coast. You will encounter a flag. Start running up the hill and enter a tomb. Your task is to follow Dillion's voice - choose a direction that will allow you to hear him louder.
This part of the task is simple - you'll find two story runes along the way. Consider using headphones, as they will help you with the task immensely. Do not worry about getting lost, as the voices in your head will revert you back to the right path.
If you went down from the right path, you'll be taken back to the initial chamber. If you've managed to follow the voice, you'll soon reach a tunnel lit by a red light.
Continue following the shouts to end the sequence and begin a short cut-scene. You've received a new fragment of the sword and can continue with the fourth trial.