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