Sopor affects the Elder Ogres, but not the Eliminators and Sirens. Using a Rusted Staff will inflict Torpor on every enemy that enters the sigil while simultaneously putting the Elder Ogres to sleep.
Grand Sopor vs 2 Garm and Greater Goblins
Use a Rusted Staff to double debilitate the field with Torpor and Sleep. Enemies are quickly slain while asleep.