An optional boss, a friendly companion and a stack of sweet loot. Who could ask for more?
Dark Souls 3: Cliff Underside to optional Demon boss
This optional boss fight and treasure un is well worth doing. You’ll find some great loot, and also advance an NPC quest. Just follow the directions here, or see the NPC guide for more information (and spoilers).
Die or fast travel, then return to the church where you spoke with the giant. Take the lift up, but run or roll off when it passes the central platform to access the middle level.