On this page of the Assassin's Creed Valhalla guide, you will find a detailed walkthrough description of the side quest The Farewell Meow.
Rewards: 1,200 XP.
In the place marked in the image above, you will meet an Anglo-Saxon woman who is mourning her dead cat, Sphinxy. The cat passed away 11 years ago, and the woman still can't get over it.
Eivor will suggest that a shrine be erected to the cat, and the woman will agree to the idea. Enter her house and pick up a bowl from the floor, then a blanket hidden behind a wooden box.
In the room behind the heavy bookcase, you will find another item belonging to the dead cat - its toy.
When you have collected all the items, bring them to the shrine under the bush. Then talk to the woman to complete this task.