To make Eyescream in Valheim, you will need one freeze gland, one greydwarf eye, and a cauldron upgraded to level three.
You can get freeze glands by killing the Ice drakes that roam the mountain biome in Valheim. However, before heading into the mountain biome, make sure you have warm clothes or make frost protection potions with a fermentor.
You can also kill ice drakes with a decent bow with little to no problems. We also recommend using fire arrows or the strongest ones you have on hand. Now to grey dwarf eyes, well, it's in the name.
To get grey dwarf eyes, all you have to do is kill grey dwarfs, and they will drop the eyes you need to make Eyescream upon death.
Next, to upgrade your cauldron, all you need to do is build one of the following cauldron upgrades as listed below.
Place all three of these cauldron upgrades next to your cauldron, and it will fully upgrade your cauldron. This will in turn will allow you to make Eyescream with both grey dwarf eyes and the freeze glands you got from the Ice Drakes.
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