|Although this article is based on canonical information, the actual name of this subject is conjectural.|
NUK UA EM ENNU, EN NETERU MESU NUT.
SEMAAIU XEFT NU, AUSAR XENRA SEBAU.
As Willow recited the incantation in flight while facing a massive demon, mystical energy started to gather in her hands. As she finished the incantation, the energy already reached its peak but its full effects were unknown as Willow lost her powers when Buffy broke the Seed of Wonder with the Scythe.
However, during the battle against the Old One Quor'toth, Willow was once again overwhelmed by the dark magics. Because of this, Willow directly faced the Old One and cast a powerful spell, presumably the same as the aforementioned spell, that was channeled through the damaged Scythe, made manifest in the form of a massive blast of immense magical power that easily matched the energies sent forth by the demon against the witch. The collision between their powers was so great that a contained explosion of their combined powers is formed in the middle of the battlefield. What constitutes its uniqueness compared to the other two versions is the fact that this spell was cast at a point when Willow was once again "dark", which could probably affect the spell's manifestation and power.
Also, during the battle Willow participated in to gain access to the Deeper Well, she cast a similar, more toned-down, non-verbal spell that manifests as a blast of powerful magical energies that can decimate multiple demons and take down single larger demons, which is further strengthened when she allows herself to tap into more power. It starts in a similar way as the spell mentioned beforehand: Willow gathers powerful mystical energies in her hands and releases said powers towards her targets. It is also interesting to note that whenever Willow casts this spell, the clouds seem to gather around her hands, as if she draws power from them, though the reason behind this is still unclear.
There also appears to be variation in how the spell manifests itself, as presumably seen in the battle against the demons that invaded Earth because of the Twilight crisis and during Willow's battle with Rack. The spell could also be manifested in the form of orbs of magical energies that are shot towards targets, knocking them back with immense force or engulfing them in massive explosions capable of leveling large mounds of land. Initiating the spell is very much similar to how it was previously described. The power behind this spell is also considerable, as even the path which it follows is affected by the sheer force behind the spell. Willow has also used a similar-looking spell against the vampires that they faced in Santa Rosita, in the form of smaller, contained blasts of magical energies that, though lacking the impact of the previous versions, is effective nonetheless.
Though all aforementioned spells are similar to each other in a good number of ways, it is still unclear if they are the same spell.