The Sayaniona's reside located in the forest in the northwest region of Solar Isle. Go back the hut of cheif. Go back behind the hut, climb the rockslide, and then head back to the bolders. The boulder will be broken by using the grapple. Next, you can use the rope that is attached to the boulder and attempt to pull it. The boulder will drop and roll towards you. Now re-attach the hook to the rope, and swing around the boulder. (Requires 55 Agility).
The light will fill the cave, and you'll be able to enter the cave of the Sa