I did some research, I personally think it's Ashe, the description is "To ascend the Mountain, I had to let go..." On Ashe's classic artwork she is the only one in the Freljord to have a ring with a glow like that, what's more on the Freljord map she is at the bottom of the mountain which matches the description.
What do you think? I personally feel this fits.
Its a gem.
Trully... outrageaous
It's very likely that its Taric. Riot said that Taric will likely be the next big rework(and that he'll come out before the next champion).
The mountain mentioned in this video is likely Mt.Targon,since we did get new Targon lores and Aurelion sol as a new Targon champ and the targon page is still missing a spot http://euw.leagueoflegends.com/en/site/mount-targon/
Add to that,the fact that 
has a joke that include a targonian and gems,that 
outright calls taric an aspect(which is the name for the targonians) and that the ring in said video does have a big gem on it and there is little doubt that it could be anything else than the taric rewrok.
I think it's Elsa. She had to let it go.
I can see either Taric or Ashe based on the gem itself. Idk, interested to see what comes next.
Pretty sure it's Taric's headpiece/crown.
