Here is the full list of all 18 Solstice achievements.
Save the day like a true hero.
Receive assistance from someone who trusts no one.
Seek magic and power hard enough.
Keep it warm and natural.
Let the Winter win.
Make the final choice.
No dog should see this...
Get intimate with an ex-killer.
Find out what happened to Lev.
Make a promise to someone you barely know.
Pay attention to Galen's mentor.
Just relax and enjoy the baths.
Play it safe when talking to strangers.
Let Yani be the doctor for once.
Bring the murderer to justice.
Leave a mark on the wasteland.
Abandon your goals.
Experience all possible endings.