The Sword of Eclipse is a new weapon wielded by the Trollhunter, created by the power of the Triumbric Stones inside the Amulet of Daylight. When the Trollhunter says "For the doom of Gunmar, Eclipse is mine to command!", the sword appears in his hand.
Such as it's counterpart, it is made of light, but in this instance it is likely to be moonlight. It appears with the Eclipse Armor when the Amulet of Daylight is activated by the user and recognizes to the Trollhunter. Currently it's abilities are unknown.