The Eiferstachel (アイファーシュタッヘル, Aifaashutahheru, lit. Eagerness Sting), also known as the Fever Spike (熱棘) is Eifer Skute's main weapon. It is also referred to as the Sting of Hollowness (徒走の棘) as in the stage title in Freudenstachel. Using it, she is capable of manipulating the location, density, and hardness of the objects around her, using them to attack. With it, she is able to transform earthly metals and flora, mainly plants, into deadly weapons in only a few seconds, such as firing batches of leaves at opponents and having several vines jut out from the ground in a spear-like style and form.

In the full version of ~Freudenstachel~, Eifer can shoot destroyable energy balls with Eiferstachel, and can even release one small one that splits into two larger ones that travel in to opposite directions. Eifer can also use another variation of her Eiferstachel attack, which is her own variation of Freudia's Freudenstachel attack, especially when she and her clones created by herself do so during Desperation Mode.