Where to find Ash of War: Ice Spear in Elden Ring

gamepur.com:

The Ash of War: Ice Spear is one of the few weapon arts you can find for polearms and is great for those who are trying to use frost damage to their advantage. Frost damage builds up on a target and eventually deals massive damage when it gets built up enough. Taking advantage of this effect is great if you want to deal a lot of damage to an enemy quickly. Here is where you can find the Ash of War: Ice Spear in Elden Ring.

To obtain this weapon art, you will need to travel north to the Liurnia region. This is the region to the north of Limgrave. You can access this area by either going through Stormveil Castle and defeating Margit and Godrick or by taking the cliffside route to the east of the castle next to the broken bridge. Both paths will lead you to the Lake-Facing Cliff Site of Grace. From there, use the tombstones sticking out of the cliff to travel northeast.

Travel along the eastern road going north. You will pass the Purified Ruins on the way. Keep following the path until you reach the broken bridge that leads to Raya Lucaria Academy. There is a Site of Grace to activate there. A little bit south of the Site of Grace is a foggy area. Visit this area at night and a Night’s Calvary boss will appear. This boss is easy to take down as long as you stay on horseback. The difficulty is increased if your horse dies or you fall off. Once the boss is defeated, you will get the Ash of War: Ice Spear.