Step 1: Go to Archdragon Peak to find a Havel NPC Step 2: Kill Havel, he will drop his weapon and greatshield Step 3: Go to the bridge above Farron Keep Step 4: The armor set will be next to the stray demon on a corpse Note that you can only get the reward from leaving a specific item once, (even if you try leaving a firebomb and then a rope firebomb) You can check out the list of other possible items and rewards below: There's more you can receive from the crow above Firelink Shrine, provided you know which items to leave.
Now you too will be able to dress like the warrior of sunlight himself - Solaire! There are four items in particular that fans of previous Dark Souls games may enjoy.