If you choose Treviso over Minrathous when the choice appears, you'll then have to figure out how to beat the Treviso Dragon in Dragon Age: The Veilguard to save the city, for the time being anyway.
The dragon is actually called Corius the Icetalon and, as the name suggests, they've got some pretty nasty ice-based attacks that can make this particular fight very tricky. Also, they're a dragon, which is hard enough on its own. Before you enter this fight, we highly recommend taking Davrin or Harding as the extra party member alongside the required Lucanis. Also, fill your pockets with health potions - you'll need them.
Now, when you're ready, here's how to beat Corius the Ice Talon in Dragon Age: The Veilguard.
For more help on your travels across Thedas, check out our Dragon Age: The Veilguard walkthrough.
Now, luckily, you don't actually have to completely defeat the Treviso Dragon here - instead you just need to wear their health enough and they'll eventually fly away. However, that's easier said than done as they have some powerful attacks and how you approach this fight will be dictated by your class.
Warrior classes will need to be up close and personal to attack the dragon, but be wary as Corius can move quite swiftly (Harding is a good ally to have on your team if you're this class because of her adrenaline buff ability). Rogues should focus on attacking from a distance and using their allies (Lucanis and, ideally, Davrin) to inflict elemental damage up close. Mage's, however, should have the advantage in this fight as they can swap to any weapons that attack with the Fire element and they can attack from a distance.
Your main focus should be to attack the weakpoints of the dragon. These points will change throughout the fight but they'll always be the part of parts of them that are glowing and purple. If you can't clearly see which part of them is glowing then it's very likely it's on the top of their head - this was particularly challenge to see and target safely.
Once you've attacked them enough to fill their stagger meter above their HP bar, Corius will be grounded with a large mark on their chest and this is what you've been waiting for. When they're like this, get up close to them and continously attack that mark on their chest to inflict maximum damage.
Once you've inflicted enough damage on them the dragon will be called away by Ghilan'nain and you'll have survived the fight - for now at least.
Also, Corius the Icetalon is vulnerable to fire-based elemental attacks, which is why Davrin and his Griffon are such useful allies to have on the field, especially if you're not a Mage. They're resistant to any Ice-based attacks so don't bother wasting your time using these.
Remember to keep your eye on Corius, if they spot you and start to leap into the air you need to make sure you're running out of the way. They'll slam themselves into the ground and try to slide crush you with their body. Dodging can work if you time it well enough, but the safest thing to do is just run out of the way.
Their next attack is Ice-based projectiles it shoots out of its mouth towards you. If you see these Ice clumps starting to form then you need to run away from them and continue running until Corius stops firing them at you, because if you stop while he's firing he can turn his head to follow you.
Another Ice-based attack to watch out for is their Ice Breath. They'll crouch low to the ground, stick their neck out and fire a dangerous beam of Ice from their mouth. They'll swing their head side to side during this attack and it can easily take your health down to nothing if you're caught. If you see Corius preparing this attack, run as far as you can to the other side of the battle area - the safest place is to be behind them, but always be mindful of their tail.
If Corius flys up into the air a bit and you see a red circle appear on the ground, make sure you're standing anywhere but in that red circle or you'll be crushed. Luckily, if you listen carefully, you should hear your companions yelling at you to get out of the way if you're at risk of getting hit. But, the golden rule is, if you're standing in red you'll be dead.
Corius really has no shortage of attacks, if you're close by they'll charge at you head first to try to headbutt you into oblivion or they'll use their claws at the end of their wings to try to grab you and push you into the floor. You can avoid these attacks by dodging out of the way, but this is why we recommend attacking from a distance if you're able to.
Remember that Corius is vulnerable to elemental Fire attacks, to focus on its purple weakspots, to dodge and run to stay out of danger, and to fill up Corius' stagger meter to ground them.
That's it for now! If you're looking for more Dragon Age: The Veilguard content, check out our pages showing you how to enchant equipment, how to upgrade equipment and how to respec if you want to experiment with Rook's skills.