Just for some examples of what I'm suggesting, flip the effects of the existing traits for easy ideas*. (*Please don't scream at me because i'm bad at balancing, these are just ideas to get my point across. I'm sure I forgot some obvious stuff that makes some of this totally OP.) Turn Holy Presence into "Unholy Wilting": At the start of each round, all adjacent enemy characters take one unholy damage. this damage is transferred to you as health, but you can gain no more than 3 in this way each turn. (This second part is merely one idea to balance the enemy controlled card cleansing effect of Holy Presence). Turn Healing Spirit into "Consuming Greed": When you play an unholy card that does damage, add one to that damage. Turn Talanted Healer into "Wrath": When you play an unholy card that does damage, add cantrip to that card and add 2 damage. (this exact style may cause issues with draw decks, but you get the general idea.) Turn Altruism into "Sadist": When you play an unholy card targeting an enemy, draw a card. (same chances for trait removal and failure) Why did I start thinking something like this would be a good addition? I like using all the evil stuff on my priest, rather than the nicey nice spells. Thing is, past a certain point in the game, the evil stuff seems to sort of stop working so well. I think it happened around level 12-ish for me. Up until then the mainstay of my fighting force was a priest using Invigorating Touch to gobble down enemies like they were candy. Life leech abilities were gradually ramping up in power for me, but then they leveled off to the point where I couldn't go vampire-style any longer. It didn't help that one of the easiest to acquire low level divine skills had Invigorating Touch on it, but I couldn't find any good unholy stuff on higher level skills aside from Accelerated Thought. Partially because of the way the traits are designed, I felt like at that point if I wanted to continue using that character, I'd have to transition them over from a predominantly unholy enemy-eating machine to a fluffy little healer, which just grated on me. It made me sort of feel cheated in the end, like I'd been mislead into thinking unholy was meant to be a valid build on it's own when really it wasn't. If possible, I'd like it to be. Added benefits could include a sort of twisted positive side to some of the handicapped gear. Demonic Miasma wouldn't be such a big deal for these priests, potentially. Meanwhile, Demonic Revenge would totally tear them a new one.
Well, talented healer works. But more wouldn't hurt. Problem with unholy priests is that lifedrain attacks gain double benefit from boosts, both more damage and more self heal. Hence they have quite limited power. It's viable later on, but requires some hard to get cards or support priest. Mass Frenzy, Horned Plates, Frenzy Aura and Blind Rage. Frenzy is hard to get, armors are unreliable damage buffs, especially as taking damage is expected. And rage is mostly for dwarves.
I was surprised to see it behave as an even trade. I sort of expected more of the drains to begin granting less and less health in return versus the damage they dealt, to even it out. It's also interesting to me that a lot of the priest buffs seem to center around buffing their damage with multiple frenzy effects. I've got a lot of that stuff, and it's interesting, but also feels a bit gimped (not to mention non-class specific, since I've got horned plates/frenzy aura on my warrior as well, I believe) compared to to the straightforward nature of a supportive priest. some of those effects are strangely glass-cannon like, as well. :/
The thing about the unholy cards is that they're already more powerful than the holy cards. That's why the holy cards have stuff that buffs them and synergies to work out. The unholy cards are, by contrast, strong, "unboostable", power-house cards with drawbacks and self-damage to boot. They do not need buffs or synergies.
I'm not sure it's a synergy I'm even reaching for. I think it's just odd that in a lot of cases, builds seem to revolve around their traits and be defined by them, but all the priest ones are centered around being what would be classically be described as a "hero"... in spite of the fact that we have a lot of evil stuff that we can draw from as well. It's like my priest is having an identity crisis and doesn't want to admit he's gone over to the dark side simply because there's no trait there to give him a focus. I'd be just as happy with anything else if it simply didn't revolve around healing or buffing. Just give it a religious flair, if that makes any sense.
I think more traits in general would be cool. I also like the unholy cards. Right now I'm running the following four items on my priest and they're pretty fun. I don't think his build is focused enough to be 'good' in multiplayer (his armor and weapons don't add to the drain strat) but he wrecks in the campaign. Superb Healer - Talented Healer, as has been mentioned, works with the drain attacks, which is just kind of gross. That's a very powerful synergy. And if you don't want to spend a major power token, there are versions of this item with weaker heal cards. Bleneth's Frenzy Charm - I realize this is a legendary that I'm lucky to have. I don't know how common Mass Frenzy is, but I do know it's totally sick with the drain attacks. The downside here is that Unholy Frenzy has nothing to do with the build. It's cool when it makes the warrior go nuts but often it's a dead draw. Hand Of Melvelous - I think this is guaranteed from Melvin's level in the campaign? It's just a bunch of drains. Wuuna's Vampiric Shroud - Just another bunch of drains on this one. What other items are good for boosting the vampiric priest? I'm sure there's a way to make it viable even without additional traits. Like, is there a divine skill that's just 3x Talented Healer? EDIT: yes there is, Focused Healer would do the trick nicely.