(2 items) When you deal direct melee damage, you have a 15% chance to call on a primal spirit that mauls the closest enemy in front of you for 12000 Physical Damage. This effect can occur once every 4 seconds.
Doesn´t say it needs to be physical damage. So concealed Weapon should proc it.
I'm wondering if ZoS just hasn't thought about this. I'm just trying to find good reasons to run concealed (pvp), which is marginal when compared with funnel health. This would have added to its usefulness (certainly fun to try) - but I guess not.