Recommended level – 43
This quest is a little more involved than the others because in order to properly complete it you must have shown the 5 virtues: compassion, generosity, honor, valor, wisdom. Each of these virtues will be tested numerous times throughout your play through of Blood and Wine, but I believe you only need to show each of them once.
To actually begin the quest, simply find a notice board with a flyer that says ‘Test yourself with the Trials of the Virtues.’ Follow the quest and go investigate Lac Ce’lavy. Talk to the hermit sitting in the middle of the lake. If you’ve shown the virtues before this point he will fight you.
Once he’s been defeated you will meet the Lady of the Lake and receive your prize.