Passive Intimidation

[Eadochas]

Recently, someone in my party decided that after he'd slain a particularly annoying enemy that he wanted to rip his bones out and keep them. I allowed this seeing as he was a Chaotic Evil character and my God does he play it well. (I'm a little concerned actually). Anyways, later on during an RP moment he asked if he could use the bones to make armor for himself. I said why not, but he would need a lot of bones and they wouldn't give him any bonus armor. He did it anyway and after slaughtering countless bullywugs he finished his caped made of spines. This gave me an idea. If someone came rushing up to me clothed in the bones of my fallen comrades, I'd be scared shitless. So I decided that he, for every piece of armor made this way, could have 1 passive intimidation point. For every 5 points gained this way humanoids of any of the types involved in making the armor took -2 to all attack rolls against him. So many people died that night.

 

[Sergeytov]

I have a similar situation going on in my game. One of the players wants to make 'skull armor' and makes this habit of collecting enemy skulls. I told him a couple other conditions, however:

1) The armor itself, with only the skulls, looks creepy but is more a flavor thing than a mechanical thing. - This is to prevent a potential slippery slope of trying to get bonuses for every little thing (and potentially break the game).

2) The upside, however, is I'd let him, with enough skulls, make an intimidation based enchanted armor at a reduced component cost (ie, using the skulls as components).

As for 'passive intimidation': Intimidation already has a 'passive' defense, that is one's will defense. Intimidation is almost more of an 'attack', which tend to require rolls to actively use. - I also ruled this spends actions in combat to use, and can get a variety of results based on the situation and versus will defenses (plus often the hostile +10 modifier).

 

[Mentat55]

There is a feat called Skins of the Slain from Primal Power that captures some of what your player is doing:

Skins of the Slain

Heroic Tier
Prerequisite: Any primal class, proficiency with hide armor
Benefit: While wearing hide armor, you gain a feat bonus to Intimidate checks equal to 1 + the armor’s enhancement bonus.

While I wouldn't let him get too much of a bonus for it (without a bit more investment than simply killing lots of bullywugs), it's pretty neat and I might offer him a feat like this one. At the very least, a +2 bonus for Intimidate checks seems warranted. You could even turn it into some sort of boon (from DMG2) that grants him an encounter or daily power that somehow plays off this creepy armor. Power level would be something along the lines of a magic item power.