Obtaining the Claim Check
The World's Finest Eye Drops must be created and delivered to Biggoron so he can work, so Link must travel to Death Mountain Summit as quickly as possible. However, he is not allowed to warp using an ocarina song. The Eyeball Frog spoils in just four minutes, so he must make haste. The easiest way to accomplish the feat is if Link plays Epona's Song and rides to Death Mountain on horseback. Once the Eye Drops are delivered to Biggoron, he will feel much better and give Link the Claim Check, signifying that he will indeed be working on the Biggoron's Sword.
Once taken to Death Mountain Summit, Link must speak with Biggoron in order to be given the Biggoron's Sword. The check proves that Link is the person to receive the sword.