Skulls

Skulls are crafting materials that are dropped by Pine Ent and are used to craft Illuminated Yulegear.

Crafting Information
In order to get the 50 materials needed to craft the armor, you need to defeat the boss up to tier #15.

In order to gain the additional 50 materials needed to craft the plus version of the armor, you need to defeat the boss up to tier #43. You also have to level the regular armor you crafted to 35 to be able to make a plus version, otherwise it will just be another regular.

You can create a 3rd armor after beating tier #60.

Alternative methods to acquire materials
These materials can also be obtained by summoning the Pine Ent at the Summoning Stone for 11 gems during the event, or 30 gems afterwards.