Although the story of the Epic concludes with Tablet XI, incredibly the Epic of Gilgamesh comes with a built-in encore / hidden track.
At the beginning, revealed through the only exchange of spoken dialogue in the entire show, Gilgamesh bemoans that his ball has fallen through a crack and down into the Underworld, and asks who will go get it back for him. Enkidu volunteers, and Gilgamesh expresses surprise at Enkidu not being dead. But with that taken care of, they agree that Enkidu will go retrieve the lost item. (Different translations call the lost object a ball, a drum, or a harp, so we have a bit of fun with that in the dialogue.)
Gilgamesh gives Enkidu a list of rules to follow to ensure that he will be able to leave the Underworld once he has entered – don’t take a weapon, don’t wear bright clothes, don’t act happy, don’t sing or dance, etc. Enkidu takes all this in, but then proceeds to the Underworld and does all the things he was told not to do. As a result, the Underworld keeps him.
Gilgamesh is bereft at losing his best friend a second time, and appeals to the gods in turn to help him. Most refuse, but Shamash, with encouragement from Ea, agrees to help. He blasts a crack into the ground, and Enkidu’s ghost leaps out, thanking them for getting him out of such a horrible place.
Finally, Gilgamesh asks his friend what he has learned about the final fate of mortals.
Enkidu relates that those who have made the most of life find an easier death, and that the happiest in the afterlife were those who had forged strong friendships and family relations, and done fine deeds to be remembered by.