Have you ever looked at a young human and thought "this is a creature that should terrify me"? I have. My unit came upon an educational facility. We had been scouting the planet, carefully, silently. The humans thought we were just tourists, we did our best to blend in. Find their weaknesses, they seemed to have many. But it was not until what we sat in that educational facility that fateful evening that convinced all of us that this colony was not to be touched. In fact, we were to avoid this place at all costs. We needed to find other prey elsewhere. We were told they were going to do a gentle ceremony for their instructor who was retiring. Something simple that the students, who had loved this instructor very much, could do for him. But when we saw the ceremony, we saw those faces, before the ceremony, during, and after. And that horrific chant, that terrifying sound. Their expressions before, one of caring, it was meant to honor their instructor, but it convinced us all, even their young were dangerous.
https://www.youtube.com/watch?v=lt6GRghrmaU -- Anon Guest
There is nothing, nothing more chilling than a group of Humans moving and chanting in unison. Regardless of the age, gender, and physical condition of the Humans involved. Regardless, in fact, of what they are moving and chanting in unison to.
Of the terrifying capacity for Human synchronisation little is more horrifying than a group of grade schoolers performing the Haka. Outsiders not used to observing such displays go through a chain of reactions that begins in, "Aaaw, cute," and ends in, "Not cute! NOT CUTE! RUUUUNNN!"
The Haka, like many things beginning in Deathworlds, is a display of strength, discipline, fortitude, and co-ordination. When performed by Human neophytes, it is once again a reminder that even their fragile young are capable of far much more destructive power than most adult Galactic Citizens.