ok here's the real facts guys
'With an impatient snarl, the predator threw down the half-mangled arm he's been working and held up his knife, as if displaying it. Lex leaned closerand examined the blade. Only then did she realize that it was not forged of metal but carved from sone bony substance like ivory, and honed to a sharp edge.
"Okay," Lex said. "It's a special blade...so what?"
Very deliberately, Scar dipped the tip of the sacraficial blade into the alien's seeping brain pan and covered it in the acid blood. Then he shook the blade over a segment of battered predator armour. As soon as the drops splahsed to the surface, the acid went to work, melting the armour'
'And obviously the sacraficial blade the predator carried was made of the same substance-alien exoskeleton, carved and honed to a razor-sharp edge.'www.thorndesigns.netdarkness of acheron