Making horns for any costume is a process. They have to hold the proper shape, be designed so that they can be attached to the head, and be lightweight enough that they don’t fall off or cause a headache. The cosplayer Lady Sundae had to keep that in mind when designing the horns that were part of her World of Warcraft Draenei Warrior costume. She shared process images showing off the stages of the horns. She began with paper templates and used a material called “polyextru” to build the layers and to shape them before covering them with black Worbla. She used carving tools to add the texture and details.
This is how the finished horns look with the costume: