Here is the full list of all 20 Saturnalia achievements.
Complete Anita's Mission
Light up all the bonfires in Gravoi
Light all the votive candles in the church
Complete Claudia's Mission
Replenish your stamina 3 times while the Creature is chasing you
Distract the Creature 5 times using the firecrackers
Flash the Creature 5 times
Team up with another character 3 times to reach a destination
Turn on all the lights inside the Mines
Use 100 matches
Collect 3 tips from the Mouth of Truth
Complete Paul's Mission
Get captured while using a phone
Use a phone 5 times to gather your companions
Read at least 90 clues
Rescue a captured character 6 times
Complete Sergio's Mission
Run out of stamina 5 times
Complete Tecla's Act
Find all the tools and consumables