Honestly, a game that is a damned shame to have to put away if you don't have time to play though in one sitting.
You don't know why you're on this journey, but you know it must be done. You are compelled to get to that mountain.
They're is no dialogue or exposition to explain. You're just a character on a foot (and often flying) journey to get to the summit.
You begin alone, but eventually ( or, occasionally immediately) you are joined by another character who is on the same quest. Will you work together, or go out alone? The companion might know more than you, and may have lessons to teach. It, perhaps you are the one to teach..
You cannot converse in the traditional ways, other than cause your character to utter a sound that must be interpreted by the other. Find a rune when you're off by yourself, and a few excited clicks will notify your companion that's something interesting is over here.
It took me a while to realize that the other character was someone like yourself elsewhere in the world who happened to be paired with you by the game. Because of the lack of direct communication, I was never certain that the other character wasn't a computer-controlled bot, until I saw them behaving in a way that I don't think a computer-controlled character would.
As you quest, you'll come across runes that cause you to obtain, and grow a scarf. As it becomes longer, it too is emblazoned by colorful runes that are sort of a life bar for your flight ability.
Communicating with fellow travelers, and other entities in the game, allow your scarf to regenerate the flight power. Conversely, there are other entities that can cause your scarf to be torn shorter.
The game takes careful steps to ensure that you don't necessarily have to have an extremely long scarf in order to progress. But it certainly is nice to have when you do.
The visuals are stunning, and the background music is haunting and wholly appropriate. Playing this game with the sound off would be an injustice, so turn it on, immerse yourself, and give yourself a good 3 hours in order to progress through the entirety. It's a wonderful thing to be able to cross into the light at the end of the game with someone that you've been working with the whole time. Walking in the light really provides you a sense of accomplishment, and you'll find yourself wanting to go back to the beginning to try again and do better this time..