While searching for Zelda, Link arrives at Eldin Volcano after placing the Ruby Tablet in the chamber of the Statue of the Goddess in Skyloft, revealing a beam of red light piercing the clouds. After traversing an underground passage and defeating a group of Bokoblins, Link obtains the Digging Mitts from a Mogma named Tyto. After hearing of a mysterious figure, Link is aided by her on his way to the summit. While at the summit, he overhears two Mogmas, Ledd and Cobal, talking about the key to the temple that was broken into five separate pieces. After using the Goddess Sword's dowsing ability to find them all, Link is able to enter the Earth Temple.
While searching for the Sacred Flames, Link returns to Eldin Volcano with Din's Power to open the Silent Realm on the volcano. After clearing it, Link obtains the Fireshield Earrings, and is able to reach the Volcano Summit and enter the Fire Sanctuary. After defeating Ghirahim for a second time, Din's Flame is embedded in his sword, making it the Master Sword.
Link returns to the volcano a third time while searching for the Fire Dragon to learn his part of the Song of the Hero. However, the dragon's power has caused the volcano to erupt, and Link crashes on the ground, waking up in the Bokoblin Base with no items. After obtaining his items, sword, and Adventure Pouch, Link reaches the Fire Dragon and learns his part of the song and the area becomes normal almost instantly.
Points of Interest
Thrill Digger area
In between two huts in the small Bokoblin camp northwest of the Volcano Ascent Bird Statue there is a bombable wall which covers the entrance to a cave known as the Thrill Digger area, where Link can play Mr. Tubert's Thrill Digger.
Due to its location, and the fact that it is the only mountainous area in Hyrule at the time of Skyward Sword, Eldin Volcano may eventually became known as Death Mountain.