Here is the full list of all 8 Refuge of Embers Demo achievements.
Play through Rithe's path in the demo
Play through all character paths in the demo
Find all five hidden effigies in the demo
Play through Lena's path in the demo
Play through Lucine's path in the demo
Play through Raisa's path in the demo
Finish the Eryn path in the demo
Find one of the hidden effigies