I'm starting to work on a Great Cusade into Horus Heresy game for a few friends of mine. I'm trying to work how the Butcher's Nails would work, I'm thinking of using the Lostok Augmentation from Into the Storm as a template. The only change I'm thinking of making is +10 Willpower roll to activate and if the roll fails you end up falling into frenzy. Any other ideas?

Implant gives a permanent +10 on rolls to resist temptation, seduction, intimidation etc and +1 intiative in combat. Free action on your turn to activate it and get the effects of the Frenzy talent (which will stack with frenzy for double effect!) however anytime a Willpower roll is failed by 5 or more degrees, the character automatically enters Frenzy and won't snap out of it untill they have taken out everything in their vicinity (allies also) or are put down themselves (KO would suffice).

I think that gives them more flavour than the Lostok implants, but sticks with the whole berserker vibe quite well.