Here is the full list of all 25 Serafina's Crown achievements.
Complete your regency with Kendal Terrace by your side
Embark on a relationship with the decadent Kendal of House Terrace
Complete your regency with Arken Jeridar by your side
Make a king out of Kendal Terrace
Begin a romance with your trusted adviser, Arken Jeridar
Complete your regency with Roza Pajari by your side
Put Roza Pajari on the Darzian throne
Kick off a romance with the fiery Roza of House Pajari
Die an early death after breaking an oath
Accumulate 10 points with Belazar, the goddess of wrath and war
Complete your regency at the side of--or perhaps between--Serafina and Reuben
Initiate a relationship with Serafina and her husband Reuben
Restore the reign of Kallias Jeridar
Complete your regency with Kallias Jeridar by your side
Make your regency a permanent arrangement and ascend to the throne
Start a romance with Kallias Jeridar, the prodigal former king of Darzia
Complete your regency by reconciling with your mysterious ex, no matter who he might really be
Allow Serafina Elborn to become the next queen
Defeat a god in a debate
Find the true killer of Queen Belatrix
Deepen your relationship with, well, someone...
Accumulate 10 points with Mallion, the god of greed and wealth
Accumulate 10 points with Picard, the god of pleasure and sensation
Accumulate 10 points with Demetral, the goddess of love and fertility
Win a debate with opponent's score at zero