Eternal Commitment is a quest received from the dying Champion Decimus at the Healers' House in the Great Market district of Aleroth during the events of Divinity II: Flames of Vengeance. He is seeking some peace of mind in his final hours. His wife has passed away during the siege and he'd like to you retrieve her favorite ring.
You'll need to gain access to Crow's Nest by completing the quest Bark up the Right Tree first. You'll find Decimus' House east of Henry and Eleanor's House and southeast of Crowell's House. Inside you'll encounter the bandit Carmina who is a target of the quest A Hunting We Shall Go Once More. After defeating Carmina and her thugs, take Livia's Ring from one of the small lockboxes.