The Envy Spear is part of the Lust Series Curse Series claimed by Motoyasu in 『Chapter 210』 of the web novel. After Motoyasu uses the Lust Spear IV's 「Temptation」 on Naofumi's party, Filo begins to lust for Naofumi which makes Motoyasu quite jealous. For some reason it is also a level IV weapon. The spear head is phallic shaped. Motoyasu uses said spear head in an attempt to take Filo's purity. Its special effect, 「Ressentiment」, sets a field with the effect of amplifying feelings of jealousy. There doesn't seem to be a repercussion for this curse series. Although Motoyasu sees women as pigs and can't understand their words, it was unlikely caused by the curse due to the fact that he started calling women pigs and ignoring them at the bar after falling for Filo.
Envy Spear IV 『c210』
Explosion of emotions equivalent to the destruction of one's heart