Visit Marianne de Ardeur in Novograd,she will give u few pre quests for Pearl Ring,1st quests is to go in Purgatory,talk with goblin there,after that she will give u 3 more quests for 3 different zones,complete that too.So when u complete them u will get quest for Pearl ring from Aidenus...
Edit
If u cant take any important quest from Marianne complet Frozen Peak....