Even without its legs, the boss could move much faster than Femradiel. Although the creature was suffering some damage from her attacks, it wasn't nearly enough to stop or even slow down the boss. At some point, the creature got close enough and impaled Ryan's right shoulder with the trident. However, Femradiel instantly healed the wound.
"Hey…" Ryan thought since he was unable to keep quiet any longer.
"My bad, my bad," Femradiel said. "It won't happen again."
Ryan wanted to know how come Femradiel could affirm that so easily, but in the end, what she said turned out to be true. He didn't realize it before, but Femradiel has been attacking the boss with the magic copies of his Immobilizing Crossbow, and the monster was quickly losing its speed. After that first attack, the boss never had the chance to get close enough for its trident to even scratch Ryan's body.