I just made a necromancer and i was playing in the catacombs when an enemy dropped a storm artifact energy + 3 unidentified. i equipped it and my energy went from 30 to 45!!!
Yep, it's most likely a +12, -1 regen thingy. If you equip it and your regen goes down by one, thats what it is. If it stays at 4, then I have no idea whats happening.