Arthradi

Arthradi is a Toa of Sonics.

De-Koro
Like most other De-Matoran, Arthradi was created in De-Koro. He lived there for a significant amount of time. However, his chosen profession was engineering, which was considered to be a "noisy" profession by his peers. The other De-Matoran actively shunned Arthradi, until the resident Turaga exiled him for "disturbing the quiet". Arthradi wandered the Matoran Universe, making a name for himself as an expert mechanic.

Nynrah
Eventually, he joined the Nynrah Ghosts. While there, he participated in experiments involving a prototype artificial Toa power, transforming him into a being somewhat similar to a Toa.

"Toa"
As a "Toa", Arthradi stayed on Nynrah, continuing to make weapons. He used his expertise in weaponsmithing to create his own Toa tools, which he named the Echo Forks.

Karzahni
At one point, Arthradi learned that there was a Av-Matoran on Karzahni who knew how to create Toa canisters. He traveled to Karzahni and attempted to locate the Av-Matoran, but ran into a swarm of Manas. He fought them, but was quickly overwhelmed. During the fight, he lost the Echo Forks, and his right arm was critically damaged. Realizing that a single Toa stood no chance against the Manas, he was forced to abandon the Av-Matoran and the Echo Forks by using his telekinetic ability to levitate himself back to Nynrah. Once there, he collapsed from the exhaustion of levitating himself halfway across the universe and was unconscious for several days. One of the other Ghosts created and installed a replacement arm while Arthradi was unconscious. When he woke up, Arthradi found he could not telekinetically manipulate the replacement arm, so he fitted it with micro-thrusters to accomplish the same effect. He then created the Boom Bulwark to replace the Echo Forks.

Brothers in Arms
On Nynrah, Arthradi learned of Vultraz' attack on De-Koro. He left the Nynrah Ghosts in order to pursue the attacker. Before he left, he created a false head wearing a Miru so that he would not be instantly recognizable as "the being with no head", changed his armor color to green, and attempted to pass himself off as a Le-Toa in case he unwittingly met the culprit. He traveled to De-Koro and inquired about the attack. He learned that although the De-Matoran had little memory of the attack, they all agreed that the attacker wore dark armor and was somewhat larger than a Matoran. He began investigating every being fitting this description, looking for the means, motive, and opportunity each of them might have had. Eventually, he determined that the Dark Hunter "Subterranean" was the culprit, and has been looking for him since.

While searching for "Subterranean", a Matoran village Arthradi was staying in was attacked by a herd of rock lions. He successfully defended the village by using a sonic pulse to stun the lions, then decreasing the pressure behind them, blowing the rock lions away. A Naming Day was held in his honor, and his name was changed to Arthradi after his tactics.

Abilities and Equipment
As a De-Matoran, Arthradi had slight traces of elemental Sonics power, such that he had extreme hearing.

As a "Toa", Arthradi had elemental Sonics powers. Like all other Toa, Arthradi can participate in fusions and trigger nova blasts. As a result of his Matatu fusing to him, he could telekinetically manipulate his own armor. He was also skilled in using his Sonics abilities to manipulate air pressure, thus creating effects normally associated with Air.

Originally, he carried the Echo Forks, which would create a sonic boom when slammed together. However, he lost them on Karzahni. Currently, he carries the Boom Bulwark, which is a large shield that can project a wall of sound. Like his arm, it has micro-thrusters so Arthradi can control it as a thrown weapon.

Trivia

 * Arthradi's original name was "Derraum".
 * "Arthradi" comes from arthra (echo, resonance) and radi (wild, gibbering sound).