When we last saw our heroes, they were resting after a long week in the Sea of Fire. They battled the great King of Serpents who despite his rage against the human race, assisted our heroes with a riddle. Let's take a peek at where they are now!
The temperature's dropping, get ready to move; these mountains can kill us, put on your shoes!
Tis winter here, much danger known; let's head to the caverns, and down to the throne.
The mountain shifted, it's face surely changed; aware of their presence, it senses the flame.
It sends down a wall, of ice and snow; RUN FOR YOUR LIVES! DON'T LET YOUR SKIN SHOW!
The mountains are dangerous, they live on their own; solitary places, where unwise men atone.
They ascend the mountain, they head towards the peak; their journey it seems, will take a week.
As each hour passes, the danger grows greater; finally the peak, they crawl in the crater.
They enter the caverns, safe so they think; descending to darkness, they must form a link.
The child ignites, his hand of fire; he holds it up high, to see what transpires.
They walk through the caverns, strange symbols of light; like craters on towers, a file with eyes.
Off in the distance, the shimmer of gold; this is the throne room, unguarded, untold.
They enter the throne room, unaware of the danger; out of the darkness, appears an old stranger.
He claims to be Loki, a devious man; he spits out a riddle, just cause he can.
The answer you'll need, which I cannot give; answer correctly and I'll let you live.
Contained in a place, but not in a play; do take your time, I've got all day.
You may find it easy, just remember, it's me; so many options, no wait, just three.
They thought for a moment, they collected their heads; if the answer is wrong, they will surely be dead.
They give him the answer, their hands on their swords; ready for battle, they'll fight off his hordes.
A flash of light, and Loki was gone; their answer correct, three letters now known.
I hope you're all enjoying the story and good luck with this one!
Hint: Loki has stated that the letter you seek is contained in a place but not in a play. This is where you have to be careful, especially when combined with there are three options. Below is a hint that should help you with the lateral thinking.
I know of three letters, resembling three; spin it or flip it, and you will see.
Once you have found it, do keep in mind; that more often than not, Loki tells lies.
Edit
I would like to apologize to the community for not giving enough detail to perceive only one answer. Many of the supplied answers were very good, and fit the story quite well; however, due to the fact that the follow up stories rely on this one and the previous stories, I have to ensure the correct answer is accepted. To those who put forth tremendous effort into solving this, and coming up with reasonably acceptable answers, thank you for your time, and I apologize for not making the riddle hold only one possible answer.
The Entire Story
I will update this section each time a new part to the story has been posted so that you can access each part quickly.