Unlike most other Noble Phantasms, the abilities of the spear are passive in nature. It does not require its name to be called upon in order to be utilized, allowing it to instantly actualize its curse of mortality upon striking the enemy. The spear lowers the opponent's maximum health limit, thus limiting healing and regeneration abilities to the point where the opponent received the injury. When Saber receives a light wound on her left arm that severs her tendons, Irisviel is unable to heal it with magecraft due to her being considered in a state of full health. It is a dangerous spear, but only its owner, Diarmuid, can stand up to the tip of Gáe Buidhe and stay uninjured while stepping into it.