Espying: Hammer of Persistence Driving the Nail of Success
"Fortunately or unfortunately for you, your struggle ends here."
Eren said and took out a water-element artifact that he had saved from his time in the duchy of Lionheart. It was an army-issued hammer that he had found to be very unique. Despite his money crunch, he had saved this hammer among all the things he had collected. He didn't include it in the list of artifacts he had sold.
It once belonged to someone who Eren later referred to as the Mute Spectator of Team Claho. Ironically, the same artifact was now going to be used on another Mute, Har Jahar. His mouth had been sealed off again by the runes under Eren's order after all.
Though the artifact was still in the Ace Rank, it served as a suitable testing apparatus for him to play with his newly gained water attainment. He channeled his water element mana and imbued it into the weapon before activating the runes etched onto it with his understanding of the way of water.