A simple quest for simple rewards down in the southern portion of the map.
The Witcher 3: Defender of the Faith
Suggested level 10
To the east of the Black Bough signpost (and far south of Hetherton) is a T-junction where you'll meet an old lady. She wants you to restore three wooden shrines to the gods.
The first one is right here and you'll put it straight right away. The second is a way off, to the south of Midcops.
When you arrive there you'll find the signpost Duan Hen and the altar is guarded by an Endrega Warrior. They are vulnerable to Insectoid Oil and Golden Oriole, and if you're under-levelled you'll struggle here. Once killed, fix the altar.
Now go south to the final altar. If you travel by horse or foot instead of fast travel you'll be treated to a nice high view of the map.
At the third altar you'll find four guys vandalising it. You can either bargain with them or beat them down, but either way you'll complete the quest here.