Rend is actually an anime-exclusive spell, having not been in the original manga version, where it is not a part of the process of defeating phantoms.
Casting Rend requires that the god have a Shinki in the form of a weapon (e.g. a dagger, a sword) in his hands, to serve as a vessel for the spell. Before "charging" the shinki with the spell's power, the god must first chant the following words (Yato and Yukine are used here as an example):
|豊葦原中国荒び垂らせぬ禍の物よ！我、「夜ト神」来たり降り、「雪器」を以って、砕き伏せ、草々の障り穢れを打ち払わん！ーー斬！(original text in Japanese)
- (*) 豊葦原中国 Toyoashihara no Nakatsukuni, literally "Middle Land of Abundant Reed Beds" is the name of the earthly realm, located between the Heavens (Takamagahara) and the Underworld (Yomi), in the Shinto creation myth. While it can mean "the world" as in the entire earth, it is usually used to refer specifically to Japan - seeing as the myth only mentions the creation of the Japanese archipelago. Due to being an obscure term for English speakers, English translation chose to use "The Land of the Rising Sun", a more well known alternative name for Japan, instead.
- (**) In the original Japanese version the targeted phantom is referred to as 禍の物 ka no mono or "being of calamity".
While chanting, the casting god makes a "halberd" shape (where only the index and middle fingers are straightened rather than clenched) with his free hand, similar to that Shinki make when casting their Boundary spell. Making the "halberd" gesture during the chant makes a bright glow emanate from its tip, which the god then swipes along the weapon in order to "charge" it with the spell.
Upon being charged, the Shinki weapon is capable of inflicting fatal damage to phantoms, and can effectively eliminate them for a short period of t the way it was a joke lol it's fine I just
- Yato is the only god to be seen casting Rend thus far, using the following Shinki:
Bishamon casts Rend with her Shinki, Saiki in Episode 1 of Season 2.