|This article contains canon information corresponding to the Tales of Arcadia franchise. That means all information in this article is true and has appeared/been validated officialy on-screen.|
The Sword of Eclipse is a new weapon wielded by the Trollhunter, which is created by the power of the Triumbric Stones when they are inserted into 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 its counterpart, it is made of light, but in this instance, it is more likely to be moonlight. It appears with the Eclipse Armor when the Amulet of Daylight is activated by the user and recognizes the Trollhunter in the process. With the power of the Tirumbric Stones, the sword is the only weapon that is capable of killing Gunmar, as well as other Gumm-Gumms and trolls.
However, it appears that it and possibly the Trollhunter's other weaponry are unable to kill wizards like Morgana since they like likely meant only to hunt trolls.