I cast Unholy Energy on one of Amy's characters in multiplayer, then waited for a new turn. The enemy discarded down to two non-attack cards (Elvish Mobility and Solid Mail), so he would suffer a minimum 4 damage from Unholy Energy at the start of the next. Then, thanks to said Unholiness, the enemy drew Impaling Stab, which would not cause any more damage. Darn. Except that the enemy somehow suffered 6 Unholy damage and died. This is in addition to 2 Poison damage from attached Bad Medicine. The only other thing attached was Impaler, so there's no accounting for this extra Unholy damage.
Similar thing just happened: enemy had Unholy Energy attached, had Bad Medicine attached, already possessed a Flight Aura in-hand (which would result in 2 damage from Unholy Energy), drew an Impaling Stab, and suffered 4 damage from Unholy Energy for no clear reason (in addition to 2 Poison damage from Bad Medicine).
I'm very sorry, but I'm being scatterbrained these days and I'm closing windows too soon. However, I think that subsequent plays show Unholy Energy is just plain counting ALL cards in hand; that's the simplest explanation.
I've just had the same problem -- it appears that Unholy Energy is dealing 2 damage per card in the character's hand. (I had maze, simple bash, and wall of stone and took 6 damage). Here's what appears to be the relevant bit from the log:
Still a problem I believe, unless I'm reading the card wrong. Code: stopTimer 0 701 BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Group=Byzantine,Event=Discard,Card=Weakened Armor BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Msg=Turn Complete BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Msg=Starting round 6 BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Event=Attachment Phase Initiated BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Msg=RattyZ drew Wall of Fire for Byzantine BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Msg=SeeverSelectCardsCommand:: selected card Wall of Fire BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Msg=SeeverSelectCardsCommand:: selected card Frost Jolt BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Msg=SeeverSelectCardsCommand:: selected card Flame Spit BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Msg=Byzantine took 6 damage BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Msg=Detaching and discarding Unholy Energy from Byzantine BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Msg=Byzantine died BATTLE LOG: Scenario=MP Cave,Room=Platouf vs RattyZ,RoomID=167593,Msg=RattyZ was defeated
