The taking of heads and scalps?

[Phaichtos]

I have seen depictions of Celtic warriors who have hung heads from their belt - presumably because they have taken them during a battle lull. Would it have been an uncommon site to see both auxiliaries and legionaries take heads in battle and hang them from their belts? I could imagine an auxiliary doing such a thing but I'm not sure about legionaries - it would make a formidable sight, though.

I'm sure we could give it some sort of credit; not all of Rome's legionaries would have been entirely composed. A man could potentially do anything in a state of 'battle/blood lust'.

- Lorenzo.

This is true. As has been pointed out, even "modern, civilized" armies have been known to do some of these things we see as nearly inhuman. In the pre-modern world full of soldiers who might have all been walking psychological cases, I don't think it would be surprising in the least to see the more "regular" soldiers partaking in such activity, and with the non-Roman auxilia I'd almost expect it.

Great point too about the hair on those Batavian helmets being perhaps based on scalps taken from defeated foes. In perspective, it doesn't seem too unlikely to me...