Last night, on Agents of S.H.I.E.L.D., Simmons crash-landed on Ego, the Living Planet. That’s where she was.
Just follow me on this…
Last night we got the episode, '4,722 Hours.' It was Simmons retelling of how she survived and what she encountered while trapped on that alien world. I got the idea going by the fact that Ego, the Living Planet is one of the more well-known planets in the Marvel Universe. Upon assuming that, I investigated and saw that both the planet and Ego also have a dual planet orbiting them.
When reading up on Ego, the pieces fell together even more. Ego has the ability to make plant like growths, which Simmons finds and uses for food. Ego can alter the minds of others to make them think what it wants, which seems to be what happened to Daniel’s friends. Ego can control the very shape of his own structure, which lead to them not being able to escape the first time as a chasm had grown larger than they had anticipated, and Ego also manifested humanoid forms to stalk and chase Simmons and her companion on the surface.
The fact that Ego is a living planet means it wouldn’t necessarily have to orbit a sun, or go near a sub - which it doesn’t most of the time, and didn’t until the very end of the episode for a few brief moments. Also the heat generated from inside of the planet, that kept them warm? The Wikipedia backs that up, too.
“Ego possesses various internal features analogous to a living organism, such as gigantic tunnels that have been compared to arteries, and a gigantic brain-like organ deep below its surface. It can heat up its internal temperature to destroy beings inside it.”
It definitely seems nearly certain that Simmons was teleported to Ego, the only question is why? Why does the Monolith, a device on Earth, transport people to the surface of Ego? Sacrifice? That we don’t know. And outside of the help of Thor and the Tesseract, how the heck could they get back?
And last, going back to a previous point, Ego can create humanoid forms to get what it wants. A theory going around now on forums is that the Monolith may have been a part of Ego, which is why when it transported you, you landed there, as a means of feeding Ego.
What if when they opened the Monolith to save Simmons, Ego realized it was in danger of being destroyed and put the idea of returning inside Simmons' head to make her find a way to bring more food? Remember, Simmons was Hope, Daniels said he would be Doom. He had no faith they would escape, ever. Maybe he didn’t actually want them to? Seems rather remarkable he survived there for 14 years and looked healthy and well.