I am present in voidwalkers and sunsingers, yet absent in warlocks. I am always in gunslingers, but more so for bladedancers, and hunters require my aid. I exist in strikers, and defenders rely on me more than any other, but titans ignore my usefulness. But i am also in evil. Atheon has me, and so does the templar. Both use me so very much, and all herald their names forever for it. However, Crota has no need for me, neither does Ir Yut, and they both sing the song of ignorance for my existence. What am I?