I had a request for strategy recommendations against each faction, but I find that only the vaguest of concepts actually apply.
So let's share those!
Fireball/Raging Inferno: The value of these cards against the Drow or Glacien factions is pretty clear, because they help you destroy the special cards the factions bring in.
Blossoming Staff Power: As nice as it can be to optimize your next turn with the Staff, don't neglect your ability to skip past Corpses or even Cultists or Freezes in the Town Deck. Sure, if you aren't playing against the Lycanthropes there's no chance of getting the Staff's nifty chaining effect, but with two or three people using it you can turn a round you'd have lost badly into a round you survive.
Heal/Prophecy: In a game with 4+ players this combo is AMAZING. With Prophecy everyone looks at their top 2 cards. Then someone with Heal lets a player draw 2 cards. You know whose two cards you want, because everyone just looked at them.
Best Skill vs Dragons: Form of Wind. Are you already on fire? You decline to take the Wound from a drawn Burn because you don't have flesh right now. Is a monster setting the first attacker on fire? You're the first attacker, and...nope. Not on fire. Be sure to risk the pain if you're taking the heavy-damage attacks like Blessed Smite or Wild Charge, though. You don't want to be stuck using those for just 1 damage if you can help it. You especially don't want to lose out on bonus effects like Leading Strike's hiring bonus or Thieving Strike's stolen Coin.
Best Skill vs Demons: Bamboozle. Cultists go from costing a coin and a magic to remove to becoming a source of income. If you use those Coins to buy walls, you can maximize the size of the Traveler deck (and thus, the amount of time before those Cultists even try to return).
Flanking and Form of Wind: Bonus damage from exterior effects (for example, Lightning Daggers or Shining Blade) is still applied to Form of Wind's genericized attacks. So if two players with Form of Wind in play and five Strikes each attack a monster, they hit for ten.
If they have Flanking in play too, they hit for NINETEEN. And they still take no Wounds.
When using Flanking without Form of Wind, remember: You won't die. Taking extra Wounds in order to turn the fight around IS worth it, especially since you gain Heroism for doing it. Sometimes you should attack back and forth even if it means taking extra Wounds.
Revitalize: If you've got three or more players, don't be afraid to buy all six of these yourself. You can play two of them to get rid of someone's Wound and make the whole team draw a card. That's your two cards for three to six cards AND a heal.
Seal: Sometimes in the early game things just go wrong too fast. If you don't have the boost, don't be afraid to basic-Seal a Shadowrift to the bottom of the deck and just make the executive decision that you'll be winning by buying Walls. Keeping monsters from gaining too many points can be the more important option, sometimes.
I've even seen a player Seal a Shadowrift to the bottom and then earn the Heroism and deckbuild into a monster-crushing engine, and then Explore his way back to that Shadowrift and Seal it for the win.
(Also remember that boost effects are additive: If you pay the boost on Seal you can Seal a Shadowrift AND throw a Monster or Power card to the bottom of the Monster Deck)
Shining Blade: It's actually pretty rare you don't want to discard this for the raw damage. When you consider that the extra Epic Attack would probably deal 2 damage, and you aren't likely to draw two Epics at once in the first place, you're usually better off dealing the hits up front and hoping you happen to have it on the same round as the 2 Epics. The one exception is if you have Epic Attacks with great bonus effects. Being able to play two Leading Strikes in one round to buy the Innkeeper for just 2 prowess? It's pretty strong.
Wall of Snow: This skill is almost criminally underrated. It can save your town as surely as Resurrect but because it's blocking instead of reversing damage the effect isn't quite as visible and players rankle at paying that upkeep on rounds when it's not saving the day. Buy two or three, and use the spares to either pay the "boost" on the first one or to buy magic Walls like the Shrine or Magic Barrier. Just...trust me on this.
Staff of Icy Blows: This is a good buy for either a heavy striker OR a heavy support, and was designed that way. For extra fun use Prophecy to toss the Prowess you'd have discarded and ensure you hit the Spell or Attack you need.
Obviously I can't cover all possible combos. What are your favorites? What are your core strategies against each faction?