(This is a guest article by kamman13, which was a winning entry in my Weekly Article-Writing Contest.)

This article uses the ideas in He-Man's control and race article, so it might be helpful to read that article first; the type of draw engine you might prefer depends if you are running a "race" or "control" type strategy. Also check out He-Man's article on card draw, as it offers a complementary analysis to this one.

Introduction

There are many types of cards that enable you to increase the number of cards you can draw per turn, all of which are termed draw engines. Also important to this discussion is card advantage, or the number of more cards that you get relative to your opponent. Incorporating some kind of additional draw engine is useful in virtually any deck for a simple reason: you need to sacrifice cards to get resources. Your natural draw is one card per turn, but if you sacrifice and play one card every turn, you use two cards per turn. This means that by turn 7 you will run out of cards in your hand - an unfortunate situation to have in any card game except Uno! Many card draw mechanisms are specific to classes, meaning that you may actually want to choose what class to play based on which class's card draw mechanism best suit your play-style.

In this article, I plan to lay out the benefits and detriments to all of the card draw mechanisms in the game, card by card. I won't get into hero-ability draw mechanisms, as those will change in 1.28 anyway.

Main draw mechanisms

Bazaar

Bazaar can be played by any deck, so the question here is less of when to play this card as what decks to play it in. The benefits of Bazaar are discussed in depth in this forum thread, but can be summarized as follows. Bazaar give you the most potential card draw for the least direct cost to you. The problem is that it also benefits your opponent. The situation this should be played is therefore when: a) your opponent has a smaller deck and you are running a "control" style deck and want them to run out of cards faster; or b) you are running a race-to-the-bottom type deck, and you think the card draw will help you do more damage to your opponent than it will help them do to you.

The caution with Bazaar is that your opponent gets the first extra draw off of Bazaar, so it can give them a card advantage. You can counteract this advantage, though: if you go first, and your opponent did not play a card on their first turn, you can play a Bazaar on turn 2. Since your opponent already has 6 cards in their hand, they still only draw one card up to their maximum of 7, and lose the card advantage. Another way to counter the card advantage is to couple a Bazaar with a Retreat the following turn to bring your opponent's hand up to 6 cards, thus denying them a draw.

Bazaar is also a particularly useful counter to most other draw engines out there like Blood Frenzy or Research. Take Blood Frenzy, for example. Without a Bazaar in play, your opponent draws 2 cards every turn to your 1; twice as many as you. With a Bazaar in play, they draw 3 to your 2 cards, only a 50% draw advantage. Thus Bazaar can serve to make other draw engines relatively less effective.

A drawback of Bazaar is that it counts as an Item, so it can be destroyed. This isn't too much of a concern, I have found, since most players are willing to keep in play an Item that benefits them. Be forewarned, though: if a player destroys Bazaar on their turn, they have ended up with a 1-card advantage over you.

Bad Santa

Like Bazaar, anyone can use Bad Santa and it benefits both you and your opponent. Therefore a lot of the logic behind Bazaar applies to Bad Santa, but Bad Santa has a few advantages. You should really only play a Bad Santa when someone has at least a partially full hand (4+ cards) and you have a mostly empty hand (3- cards). In this situation, Bad Santa actually gives you a card advantage, since you gain more cards than your opponent. Bad Santa's unpredictability means that your opponent can't plan for its use, as they can with a Bazaar, making it more useful to you than them. The disadvantage is that it doesn't have the potential to give you as many cards as Bazaar does, so if you really need a continual source of cards, a Bazaar might be a better option.

As an additional plus, Bad Santa is a an ability, so cannot be destroyed like Bazaar can be. In this sense, it is a more consistent draw engine than Bazaar.

Note: if an opponent has 4 cards in their hand, then a Bad santa will give them all three cards, but now your opponent has a full hand, which means they miss their next turn's draw and you effectively get a 1 card advantage.

Research

Research is a mage specific card. This card is a quite expensive card draw, it takes 2 resources to play it, and another 2 every time you want a card. In this sense, it essentially does the same thing as Bazaar, but instead of giving a card to your opponent, you pay two resources a turn. To its advantage, you only have to pay the cost when you need to use the draw engine (compare this to Blood Frenzy). This card is really only useful in a "control" style mage deck. These are slower decks, where you can afford to be spending resources on card draw rather than spells or allies. In a "race" style mage deck, go with Bazaar, so you don't have to waste the resources on card draw.

Blood Frenzy

Bloody Frenzy is a warrior card, and for good reason: it synergizes well with Enrage. Like Research, this card does what bazaar does, but you pay one life per turn to prevent your opponent from drawing a card. This is typically considered an excellent draw engine, because warriors often have allies or armor in play, distracting the opponent and shielding from damage. If you are winning board control, between your allies and weapons, you should be able to destroy your opponent long before Blood Frenzy takes you down. But Blood Frenzy does mean that you are inherently playing a "race" type deck; barring all other concerns, Blood Frenzy will cause you to lose, although it is a slow loss. "Control" type decks with a lot of item destruction, board wipes, and delays (Rain Delays, Freeze, Snow Sapphire) can use Blood Frenzy to your opponent's advantage, as all of these sorts of cards delay or extend the length of the game, neutralizing your increased card draw for a few turns and forcing you to soak some Blood Frenzy damage.

As a bonus, Blood Frenzy attaches to your hero, as opposed to other draw mechanisms which function as items and can therefore be much more easily destroyed. Unless you are facing a Jericho, you are pretty much ensured to keep your Blood Frenzy active for the whole game.

Wizent's staff

Personally one of my favorite draw engines, Wizent's Staff is a priest specific item. It functions like Bazaar, giving you a card per turn, but the cost for preventing your opponent's draw is one shadow energy. As priest's (currently) don't have great use for their shadow energy, this is probably the cheapest option in the game to get continual card draw. It comes with a slew of drawbacks, though: it costs more than any other draw engine to get in play, and, as a weapon, it can be destroyed by an item destruction card or simply by being used four times (for attack or defence). This means its use is rather limited to situations where you can have some semblance of board control, because the last thing you want to happen is to pay four resources and one SE to get only one card draw before it gets eliminated right after it comes into play. This also makes it less effective against hunters with Rapid Fire, as you'll only get two turns of draw from it if the hunter attacks your hero repeatedly. On the plus side, you can always use the staff as a weapon, to wear out an opponent's weapon or armor, or to land a finishing blow on an ally.

To effectively use Wizent Staff's as a draw mechanism in priest decks, you need several copies of it in your deck, since you can count on one staff to last all game, or you need to bolster the staff with Bad Santas or Bazaars. This means, as a priest, you will be dedicating significantly more of your deck to card draw than if you played another class.

Belladonna

Belladonna is a shadow ally card that functions as a nice draw mechanism, especially when coupled with Gravebone's resurrection. This is a high cost ally clocking in at four resources, and, at only two life, she's likely to be dead the turn after she has been played, but that doesn't make her useless - far from it. At four attack, Belladonna has to be killed the turn she comes out, or she does some beefy damage. Therefore, at a cost of 4 resources, you get a new card and you create a distraction that the opponent has to deal with, rather than attacking your hero, for instance. When played on a full board, Belladonna almost acts like a delay card, giving you a new card and delaying the opponent's action for a turn (assuming she dies). Once you realize it's ok to let her die, this becomes a pretty nice card. If you're running a mage deck, you can even couple it with a Portal for some damage+a delay+card draw.

As a pseudo delay card, I'd say Belladonna works more as a "control" type deck card, but, when coupled with a Portal, it can be used in a "race" type deck.

Alternate Draw Mechanisms

These cards aren't as dependable for card draw as the "main" card draws, but are more useful for grabbing a useful card or two, or messing with your opponent.

Here Be Monsters

Not a bad card, but not really a good card either. It gives you one card for a cost of three resources, which - compared to card advantage Bad Santa can give you for instance - isn't really all that great. If you at least play it at a time when you can trigger its secondary effect, and knock down the opponent's resource pile, it becomes slightly more reasonable. You essentially force your opponent to sacrifice one more card to get back to the same point they were before, which "shorts" them by a card, giving you a +2 card advantage. Even considering this, a two card advantage for three resources isn't that great of a deal.

Reconnaissance

I consider this card similar to Here Be Monsters: it's a 3-cost for 1 draw, but, with enough allies in play, the +1 attack side effect can make this useful. Still not enough draw to be a staple of a Rogue deck though.

Wrath of the Forest

A great Wulven/Hunter draw engine that I have not spent much time employing yet, so my thoughts are speculative. With a durability of 4, it should stick around to give you at least a few cards: I'd say at a cost of 4 you'd need at least 2-3 cards to make it worth your while. Which means that it should only be played when you have several allies in play. This card is nice as it forces your opponent to choose between attacking your allies and giving you cards, or letting your allies live to run down the durability of this armor. Coupled with a weapon, this can be a tough decision for an opponent. At the very least, I'd say this is a situationally dependent draw card, but very effective in the right situation.

Ill-Gotten gains

A great Rogue-specific draw engine, at, in my opinion, way too high a cost. Whenever you kill an opposing ally or item, you get to draw a card. This is an awesome draw engine for many decks that rely on allies or weapons, and synergizes well with other Rogue cards like Stop Thief or Assassination which take down opposing allies and items. Against a DD mage deck though, this card is pretty useless, so it has to be played with a knowledge of your opponent's strategy. The problem right now is that, as a Rogue, by turn 5 you either have complete board control and are going to win whether you play this card or not, or you have lost or are close to losing board control and can't afford to spend valuable resources playing this card. With more cards or changes to Rogue decks, this will hopefully change.

Stop, Thief!

Another great Rogue card that fails for the same reason as the card above (turn five is too critical for this card to be played). This card give you an extra resource, which by our Here Be Monsters logic is like giving you an extra card. Additionally, this is a resource on a turn that you probably already sacced a resource, giving you a clear resource lead over your opponent. So for a cost of 5, you destroy an item, get 1 card advantage and pull ahead on resources. I think this card is a great deal, but Rogue decks just aren't strong enough to support it yet.

Gravedigger's Cloak

A nice Hunter/Rogue draw engine, though at a steep price. It takes 5 resources to get into play, and costs 3 SE per draw. Compared to Wizent's Staff, the card draw isn't nearly as good, and it sits at one less durability, so is thus easier to get rid of. What it has going for it, however, is that it draws from your opponent's graveyard, which is presumable a limited selection of highly valuable cards. Thus, this is a good way to get you ONE strategic card at a high cost, but not an effective way to get MANY cards into your hand.

Night Prowler

An awesome card, in the right circumstances: you grab a card from the opponents hand, giving you a one card draw, or a two card advantage compared to your opponent. For 5 resources, it's really only useful if you can use it more than once, and, at one durability, that makes it very situational. This can only happen when a) your opponent has no weapon in play, and b) your opponent has no allies in play or you have an In The Forest. Rapid Fire also makes it more useful, for obvious reasons. Because so many conditions for this card need to be met, it's really only useful as a late-game strategic maneuver once you've set up the right conditions, rather than a reliable whole-game card draw.

Transference

A nice Elemental ability, allowing you to draw a card from your opponent's deck. This is supposed to disrupt your opponent's strategy more than being a reliable source of draw, since 3 resources for 1 card and no card advantage is a terrible deal. It works especially well in a "control" style deck, in which you are trying to run down your opponent's deck.

Dimension Ripper

A Warrior and Elemental weapon that allows you to draw a card from each other's deck. At three durability, this gives you and your opponent up to three cards for 5 resources. Not great card draw, but reasonable since you get 6 damage out of the weapon (3 attacks at two damage). Still, like Transference, these cards come from your opponent's deck, so it's more of a way to mess with your opponent than give you the cards from your deck you might really need. In fact, you could end up losing cards from your deck that you really need, so many people treat this card as one for "fun" decks only.

Interesting note: I had a warrior use this on me once. I cast one of the allies I got from the trade into play. He then cast Retreat on the ally, which put the ally back into HIS hand, as he was the original owner of the ally. Now, that's some nice sneaky card draw.

Tainted Oracle

I have yet to experiment fully with this card, but could find it's used most frequently in priest or mage decks, where two-sided board wipes are quite common. As a draw mechanism, you are getting 2 cards for 4 resources, which is rather steep, but it does double as an ally that can do 2 damage. If the opponent has to take the time to destroy it, then four resources for a delay and two cards is more than worth it, and certainly beats out Belladonna. The problem is that, at only two attack, it can be ignored for a while, meaning you might not see your card draw for a few turns, or ever if the opponent has Crippling Blow and you don't have a board wipe. I think cards like this, that you don't mind sacrificing to do a little damage to a beefy opponent, will become more and more useful as the number of cards in the deck expands. I'm still holding my breath on this one though - it could be a major draw mechanism, soon enough.

Lily Rosecult, Shadow Knight

A human and shadow ally, respectively, that effectively give you card draw by putting another card in your hand, though from your graveyard rather than the draw pile. Their use is pretty self-explanatory as a strategic, late-game play, but they can't function as a primary draw mechanism for this reason. I'll also add that, at one less resource, I find Lily a much better deal.

Campfire Stories

This card can hardly be considered a draw mechanisms, as its function as a heal card is much more useful a consideration than 1 card for 2 resources. Now that there are beefier monsters in 1.27, this may see more use, but I still think the primary purpose of this card is to heal. The draw mechanism is just a nice little side effect to make the heal worth your while.

Cobraskin Wraps

A priest and hunter armor, when it comes into play, you both lose a resource and you gain a card. Using the logic described above in Campfire Stories, losing a resource acts as one card that was in your hand that went to waste, so this card gives you no card draw (+1 for the draw, -1 for the resource destruction), while giving your opponent -1 card draw. Thus, you get 1 card advantage for 4 resources, and an armor to boot. Not too shabby, but not too great.

Surprise Attack

A pretty worthless Hunter card that I've never seen played. At 3 resources, it gives you one card for every enemy ally in play. I'd say you need at least 3 enemies allies in play to make the cost worth the card draw: 4 or 5 being ideal. But if you're playing a Hunter and the opponent has that many allies in play, you've got bigger problems than card draw.

Conclusions

Currently, the only way to have a competitive deck is to feature one of the main draw mechanisms listed above. Notice that, besides Bazaar and Bad Santa, the other major draw mechanisms revolve around Warrior, Mage, and Priest classes, which are the main competitive classes right now for this reason. As the card list expands, though, and you have many minor options for card draw, I think we can see decks that can get away with enough card draw from minor draw cards sprinkled and synergized throughout the deck. (I'm thinking Rogues in particular here.)