Source: Exotic engrams; extremely rare world drops.
Lore
The Hunter leaned on the sill of the broken window, poking at the upended beetle lightly with the barrel of her gun, rocking it little by little until it got its footing and flipped itself. As it crawled away, the crouching Titan pushed himself up, grunting as he did. "I was worried you'd shoot it for a sec. The poor guy." "Nah, I'd not do that to ya. You know what they say about Titans." "What do they say about Titans?" "Uh, well, you know…" He crossed his arms, and a faint sparkle like coals burning out shimmered across him. "Tell me." She raised her hands in surrender. "All right. It's a joke so don't knock me for this one. 'Titans are like beetles, impervious until they've been knocked on their back.' Erm, all in good taste, of course." The Titan cracked a smile and then began to laugh. "I see why Hunters wear that beetle armor then!"