The dueling feature in Hogwarts Mystery is, as of now, limited to certain events. The events are available for a limited amount of time, and the object is to win a certain amount of duels to unlock rewards in the form of gems, coins, energy, and/or exclusive clothing or accessories.
The exact shape of the dueling events seems to vary, we have seen events with one, two or three tickets, and versions where the tickets don’t replenish if you lose them, as well as versions where they do replenish. If they replenish, that could take anything from a few hours to a day or so. If you lose all your tickets, you will see a timer that counts down to when they have replenished. If there is no timer, your tickets will not replenish.
Regardless of how many tickets you have, they serve the same purpose. When you win a duel, you retain your tickets, and earn one point towards the rewards in the event, as well as either energy or coins. When you lose a duel, you lose one of your tickets.

In all events, you have had the option of using gems to buy more tickets. Gems are precious, and you probably want to save them for other things, so here are a couple of ways to increase your chances of winning.
Dueling 101
It is not unreasonable to compare a duel to a game of rock-paper-scissors. You can choose one of three stances–Aggressive, Sneaky and Defensive–where Aggressive beats Sneaky, Sneaky beats Defensive, and Defensive beats Aggressive.

When you have picked a stance, it is revealed what your opponent picked, and either you win, you lose, or it’s a draw.
If you win, you get to pick one of the spells under a certain stance (see table below), and trace the spell on your screen to cast it. If you fail the tracing, you are offered however many extra chances you need to get it right.
If you lose, your opponent will instead get to cast one of the spells under their stance.
If you draw, the one of you who has the least health will heal by 2 points.
Unbalanced stats
In the first few events, the dueling was quite unbalanced. Your opponent would start out with 80 health, whereas you only had 40. This meant that your spells appeared to do less damage to your opponent, than theirs did to you.
This no longer appears to be the case, in the last couple of events, your health and the opponent’s has been the same (40 for both of you).
Your opponent is, as of now, always AI (Artificial Intelligence). The avatar and Facebook profile picture belongs to someone who plays the game, but a computer is controlling them in the duel. They don’t always use the most effective spell in their arsenal–indeed, they have been known to heal themselves when their health is already full.
Your first opponent will have lower stats (attribute points) than you, but the next opponent will be closer to you in stats, and soon you will be fighting opponents with the same stats as you.
Stats are important, as they can increase the effect your spells have. Each spell is associated with a certain attribute (again, refer to the table below), and for every extra point you have on that attribute, your spell will do 2 bonus damage. So if your Knowledge is 12, and your opponent’s is 10, your Expelliarmus will do 4 extra damage.

Bear in mind that if you are a low year but have high attributes, you will be pitted against players with similar attributes as yourself. This means you may be fighting someone who is a year or two above you, and who therefore has access to a lot better spells than you do (for example Depulso). So if you have leveled up your attributes a lot, but not progressed the story correspondingly, your duels will be more difficult.
How to win duels
With the basics out of the way, here are some tips and tricks on how you can win as many duels as possible. Bear in mind that none of these strategies are 100% guaranteed, but they do increase your chances.
Finding the pattern
One way to win is to find which pattern your opponent follows, and counter it. There appears to be two different kinds of opponents, with different patterns to their dueling.
The Spammer
In your first few duels, your opponent is likely to pick one stance over and over again. The approach to this opponent is quite easy. Once you have figured out which stance your opponent is most likely to use, just use whichever stance will beat it. So if your opponent is Aggressive most of the time, you can pick Defensive and almost always beat them.
The Cyclic Shifter
Your later opponents will likely be trickier to find a pattern to, as they will not just use one stance, but alternate between two or all of them. Even these opponents do have a pattern, however, and if you can find it, you can counter it.
Spamming Aggressive
Note: Some comments on reddit indicate this is no longer effective. However, another comment disagrees. Depulso does less damage, but it’s still a strong spell.
If you want an easier way to win, instead of trying to find a pattern, you can take a page from the Spammer’s book. Especially if you have access to Depulso, this is a very effective way to win.
The strategy is simple: choose the Aggressive stance, and pick Depulso if you win. When you are around half your health, you may want to switch to Defensive to heal yourself. The Wiggenweld potion is your best bet for healing, as it guarantees 15 healing, whereas Episkey only guarantees 10, with a chance of an extra 10.
The Aggressive stance is also the best choice to make sure your opponent has the least chance of doing damage to you. If your opponent wins with Defensive, there is a chance they will heal themselves instead of hurting you. Or they will pick a spell that will hurt you, but the Defensive spells are far less effective than the Aggressive and Sneaky ones.
Don’t be Sneaky
The most powerful spell, as of now, is Depulso, which deals 17 damage. Depulso is an Aggressive spell, so if you play Sneaky and lose, there is a risk that your opponent will hit you with Depulso. This does a great deal of damage to you, so unless you have figured out your opponent’s pattern and are certain they will not choose Aggressive, I advise you to stay away from the Sneaky stance.
The different dueling spells
For easy reference, here is a list of all the moves you learn in year 1-4, their effect and which attribute they are associated with. Choose wisely.
Aggressive
Spell | Year | Effect | Attribute | Chance |
Throw Vial | 1 | 10 Damage | Courage | – |
Expelliarmus | 1 | 10 Damage | Knowledge | Stun 1 turn |
Incendio | 2 | 5 Damage | Courage | Burn 2 turns (-10 each) |
Depulso | 3 | 17 Damage | Empathy | – |
Confringo | 4 | 5 Damage | Empathy | Stun 2 turns |
Sneaky
Spell | Year | Effect | Attribute | Chance |
Throw Vial | 1 | 10 Damage | Courage | – |
Rictusempra | 1 | 5 Damage | Empathy | Stun 1 turn |
Flipendo | 3 | 15 Damage | Courage | – |
Immobulus | 4 | 10 Damage | Courage | Stun 1 turn |
Diffindo | 4 | 6 Damage | Knowledge | Bleed 8 turns (-3 each) |
Defensive
Spell | Year | Effect | Attribute | Chance |
Throw Vial | 1 | 10 Damage | Courage | – |
Wiggenweld Potion | 1 | 3 Heal +Heal 2 turns (+6 each) | Knowledge | – |
Episkey | 2 | 10 Heal | Empathy | Heal 2 turns (+5 each) |
Pertificus Totalus | 3 | 5 Damage | Knowledge | Stun 2 turns |
Bombarda | 4 | 5 Damage | Courage | Burn 1-2 turns (-10 each) Stun 1 turn |
Credit to Nevac14 for helping out with some of these tips, and to Witches Unite for letting me borrow a picture!
Wait, they are all AI? I knew something was up!