Trials of Merlin is the fifteenth main quest in Hogwarts Legacy. This walkthrough will guide you through all objectives of the Trials of Merlin Main Mission.
Requirement: having completed The Girl from Uagadou, Level 4
Reward: 260 XP, Merlin Trials
Quest Info: Nora Treadwell and I defeated some Ashwinders who were looking for me near Lower Hogsfield. Afterwards, Mrs Treadwell showed me her research on something clued the Merlin Trials and I was able to help her solve on the puzzles. Now that we know how they work, I should try to solve the ones I encounter.
Objectives:
- Help the Stranger
- Defeat the Thieves
- Speak with the Stranger
- Get the Mallowsweet from the Trunk
- Solve Merlin’s Trial
- Speak to Nora Treadwell
Starting Location: Trials of Merlin
We met Natty Onai outside of Hogwarts, in a hamlet village called Lower Hogsfield. After talking to her, we’ve heard the screams of a stranger from a nearby camp. Whomever could it be?
Help the Stranger
Proceed to the nearby mission marker to find a woman being harassed by two thieves.
Defeat the Thieves
Defeat the thieves, using all of your spells in your arsenal and don’t forget to press 
for Protego when the prompt appears. After the first two thieves, three more scouts will appear, one of which will be protected by a red shield that can be expunged with Incendio. During the encounter, a Duelling Feat will appear asking you to complete the battle before the time is up. Don’t worry if you fail.
Speak with the Stranger
Once all thieves and scouts have been dealt with, speak with the stranger woman.
Get the Mallowsweet from the Trunk
Approach Nora’s trunk by her tent to collect Mallowsweet.
Solve Merlin’s Trial
Press 
/ 
to place Mallowsweet where the quest marker is and then cast Incendio on the pyres around the area.
Speak to Nora Treadwell
Now speak to Nora once more to end this quest.
This finishes Trials of Merlin in Hogwarts Legacy.
Next Quest (depends on your house): Ollivander’s Heirloom (Ravenclaw) / The Hunt for the Missing Pages (Gryffindor) / Prisoner of Love (Hufflepuff) / Scrope’s Last Hope (Slytherin)
For all other quests refer to the Hogwarts Legacy Walkthrough.
Instead of finding myself on the quest for Ollivander Heirloom, I find myself on another journey to Azkaban prison.
This is normal because you’re Hufflepuff.
I can’t finish this quest. I defeat the first two but nobody shows up after that and we just stand there awkwardly. Anybody else having this issue?
I had the same issue. I found that if you leave her and then abandon the quest when prompted that it will fix the issue when you restart it