Claymore with a passive that deals an additional damage when you attack an enemy, by dropping an ice, with increased damage if the enemy is affected by Cryo. The ice deals physical damage, and does not apply Cryo. The secondary of the claymore increases physical damage, which might not benefit Chongyun that much.
You obtain 1 for free as a reward after you unlock the ruins by interacting with 8 stone tablets, as well as finding 3 box key items.
This stone tablet is at the top and center of Dragonspine, close to the Peak of Vindagnyr(domain) door entrance. You need to unlock it to be able to reach the stone tablet. If you've reached the top of the mountain, you can place a portable teleport waypoint at the top of the floating rocks so you can reach many other places easily.
South of the domain area, there is a place with an inactive Ruin Grader. It's much easier to get here by gliding from the top of the mountain. Once you're there, the stone tablet is to the side of it. You don't need to defeat the Ruin Grader, but defeating it will give you 3 treasure chests.
In the location shown above, there is a mini puzzle where you simply have to guide the warming seelies to activate the ruin braziers. The activated ruin braziers will only last for a few seconds, so you have to guide another warming seelie on the other side so the braziers all stay up at the same time.
Once the lower area is open, there are 3 warming seelies. Similar to the one above, you have to make it so that the braziers are all lit at the same time. You simply guide the one in the front and make it pass 1 brazier, before you touch the second one, then let it pass 1 more brazier, then touch the last seelie. Once it's done, the Ruin Grader will become active. Defeat it to open the gated area with a scarlet quartz. Use it to melt the ice on the other side of the Ruin Grader and interact with the stone tablet.
This stone tablet is inside the locked door where you have to get 3 boxes to open. To reach this area, teleport to the Statue of the Seven, and head south, close to where the teleport waypoint is. You can also get there by using the teleport waypoint, but then you have to climb up quite a distance to get there. Interact with the device near a circle door, and hand in the 3 boxes to open it.
Close to Albedo's camp, head to the marked area shown above. There is a stone tablet near the edge, where it's also accompanied by a Ruin Grader. You have to defeat it to be able to interact with it.
To the side of the stone tablet, there is an area where you can climb up the stairs and see some wind fairies. Use the fairies to create an upcurrent into a small tower with a luxurious chest. The chest contains one of the key items required to open the door later on.
This area is also part of the Peak of Vindagnyr domain unlock. Start by activating the device with the warming seelie, it will then guide you to the required pattern that you need to activate the devices. You will then be forced into a difficult fight against 2 Ruin Guards, and 1 Ruin Grader after you defeat the 2 guards. There are 4 ruin braziers which activates on its own 1 at a time. Be sure to pay attention which one is currently active to properly manage your sheer cold status.
East of the Frostbearing Tree teleport waypoint, there is an altar like area with some unlit torches. Light the unlit ones using any Pyro attacks and a machine enemy will appear. Defeat it so you can interact with the stone tablet.
The last stone tablet is inside the area with the sealed device. Teleport to the Statue of the Seven, turn around and go into the circle to the lower floor, then head south to get to this location.
3 Boxes Locations
In the small island, there is a sword that you can interact for a time trial challenge. Defeat the 3 abyss mages within a certain time to reveal a luxurious chest, containing one of the boxes.
On the other side of one of the place with a stone tablet accompanied by a Ruin Grader, there is a broken down tower. Climb up the stairs and interact with 3 small wind spirits (anemograna) to create a wind upcurrent and open up the luxurious chest.
The one close to the teleport waypoint, there is a tombstone where you can place down some sweet flowers. After giving the items, a luxurious chest will appear, giving you one of the boxes.
After you've interacted with all 8 stone tablets, interact with the device in the ruins close to the Statue of Seven to open the door. Once inside, light up all 4 unlit torches in corners of the room, which will trigger a mini cutscene and puts a the Snow-Tombed Starsilver, and get the achievement "Glacial Steel". Opening up the treasure chest in the room will give you the blueprint to craft the claymore.