Thanks to the spell that was cast upon your boots some days ago by a fairy (as a practical joke), your captor was not able to remove them. And if enough fairy flitter still remained from the spell, you would be able to cling to the wall.
You go for it. You bound to the wall and you're there in seconds. As you start t climb the wall, you catch a draft from down the dark tunnel; a horrible stench that nearly knocks you over.
That's no Troll.
Your hands and feet stick to the wall with fairy magic, and you climb up and up, toward the ceiling of the chamber, which is higher than you expected. Then you wait.
Great footsteps grow louder, causing rocks to fall from the ceiling. Just then, you remember legends you had been told when you were a child. They were ridiculous legends; everyone assumed them to be jokes of some kind. These were the legends of the Bear-Whale.
Now you know it is real, as you stare down at the massive monstrosity from above.
It knows you're there through its high-powered natural sonar. Through the chapped blowhole on its back, it shoots a sudden spray of acid directly toward you. Your skin melts... then your bones.
You're dead.