The first xenos dissolved into a cloud of acidic mist. The second melted into the mud. The third… was already behind them.
Roth smiled a thin, terrible smile. “The Mark of the Xenos describes the old predators. These are the new ones. Stealth strains. Infiltrators. They carry no pheromone signature. The Deathwatch’s auspexes won’t see them until it’s too late.” Warhammer 40K - Mark Of The Xenos.pdf
His savant, a pale woman named Helix, held a trembling auspex. “My lord… the bio-signature is wrong. This ship fell in 789.M41. But the cellular decay suggests… three months.” The first xenos dissolved into a cloud of acidic mist