Lupus Boreas, also known as Andrius, is one of the weekly bosses in Genshin Impact, and is unlocked once you complete the story related quest at around Adventure Rank 21. You can keep doing the fight multiple times because the boss respawns, but you can only claim the rewards once a week, and it costs 60 resin to be able to pick up the rewards.
Boss fight preparation
Andrius is Cryo element, and it is immune to both Anemo and Cryo type damage. However, you can still apply Cryo element to it, and also cause Swirl reaction. His attacks can also be quite difficult to dodge or i-frame, so it's recommended to use ranged characters instead. If you only have melee characters to work with, then it's recommended to bring characters that can help with some survivability.
Ningguang or Fischl works quite well against the boss because they're ranged and deals good damage. Ningguang's attacks are Geo element and causes "Crystalize" reaction, giving you a Cryo shield when you attack Andrius.
Other options to help with some survivability are characters that can give you shields. Diona can give you a Cryo shield from her elemental skill, and Beidou's elemental skill gives her a shield with some burst damage potential. Other than that, any Geo elemental character like Noelle can be good because of "Crystalize" reaction.
After you assemble your team, you can use some food buffs to help with the fight. Cook some food that will help you recover your HP so you can use it in battle, and eat food buffs that gives you some attack and/or defense increase. Food buffs don't stack with the same food type, so you can't eat multiple attack type food for huge attack increase, but you can eat it together with a defensive type food.
Andrius has 2 wide range claw attacks. The first is pretty quick, but it doesn't hit the area behind. The second one is where it creates an ice circle beneath it, and does a 360 degree attack that hits quite hard.
Ranged characters can shoot from a safer distance during these attacks, but if you are using melee characters, try to stick to his back legs. Get some distance from it when it does a hop and turns to you, then wait until it's done attacking to go to the back legs again.
Try to watch out for its ranged attacks as you get away from it. When it creates an ice circle that's not underneath it, it means that Andrius will jump to that location. Occasionally, it will also do a quick dash attack that's difficult to dodge because it's hardly telegraphed.
Andrius can also do a special attack, where it creates an ice ring on the edges of the arena that deals damage over time if you step on it. Andrius will then run around the arena in a circle briefly, until it stops for a second before it charges at you. The move will end when it creates an ice circle in the middle of the area, showing you that it will leap there and deal damage.
You are able to stop its charge by using an archer and shoot a charge shot when it stops moving, or as it's charging at you. If you are using Geo main character, you can place a rock in front of you so that it deals damage to the boss when it charges. It will go through the rock so you still have to dodge, but it's a nice way of dealing damage when it's doing this attack.
Once it reaches around 50% HP, it will do the special move where it runs around the circle of the arena. After the move ends, it will empower itself, becoming white and also bigger. It will then be followed up with a casting animation where icicles will start to drop at your location every few seconds.
In this phase, Andrius will not be moving from its spot in the center of the area, but now has several new moves, but they're all mostly ranged. The wind blades can be dodged by going in between the blades, while the ice ranged attack in a line is easy to dodge because it's telegraphed. If you get too far from it, or stay away from it for too long, Andrius can do a howling attack that deals damage over time to the entire area, so try to not stay away from it for too long.
The tail area can sometimes be a safe place to attack, but you will have to try and dodge the tail sweep that is telegraphed when it lifts the back leg before the sweep. It's recommended to unleash all your burst to finish the fight as soon as you can, because it can get difficult to dodge all the icicles, wolf spirits, and Andrius' attacks.