The vampire is one of the special races in Desktop Dungeons. It is unlocked by clearing the Crypt with an Assassin. Vampires gradually lose health on their own, but they drain blood to heal themselves, be it from living or fallen creatures. Additionally, they cast spells using their health rather than their mana.
Life Steal causes you to get back a percentage of your Total Damage you dealt as Health when you use a melee attack. So if you hit a monster for 50 damage, you'd recover 12 Health with 25% Life Steal.
Vampire is tricky at the start; once you've gained a couple of levels though, your increased Health and Damage makes taking on almost any enemy a breeze. However, First Strike does not let you go before other enemies with First Strike, and the lack of regeneration means that Gorgons can pose a minor threat if you're not careful. The increased Base Damage means that effects that increase your Damage Bonus are even more potent though.
Once you get BURNDAYRAZ, the Vampire can beat bosses almost immediately, because they draw mana from health, and at level 4, you can have, say, 52 health, which gives you 6 casts: 52-6-7-8-9-10-11=1, where each cast costs one additional HP, for a total of 96 damage, which is enough to take out most level 7 monsters, possibly level 8 if you can take advantage of First Strike. Note that the Health that you'll spend casting BURNDAYRAZ until a monster can be killed instantly with First Strike is usually much less than the amount of Health that you'd lose by allowing the enemy to hit you.
Vampire is the only race/class in the game, that don't need exploration control - actually, you should explore as much of dungeon as you can. After first exploration you could start attacking - even with 1 HP you can kill a bunch of monsters. Level up will heal you; from this moment you can attack monsters 1-2 level higher than yours.
Try to save bloodpools for later but use your potions early—at high levels you usually wouldn't need them (except for the Factory). Due to the Vampire's nature, neither BLUDTUPOWA nor HALPMEH is of any use, they should be converted on sight.
If you are lucky enough to find CYDSTEPP and push your Life Steal up high enough, you can set up for boss battles by leaving as many opponents (without First Strike) as possible one hit away from death. Hit the boss, kill someone to regenerate enough HP for CYDSTEPP, cast, then repeat until the boss is dead.
Perhaps ironically, Vampires are arguably more likely than other classes to benefit from worshiping a god. Since you'll be exploring as much of the dungeon as possible from the get-go, you're more likely to find most or all of the available shrines before even advancing to Level 2, which means more opportunities to gain Piety; the odds that you'll discover a shrine too late in the game for it to make any difference are also vastly reduced. Knowing all of your options before picking a God is tremendously helpful, especially if you take into account the items available from the shops that you will likely have discovered by this point as well.
Be aware that both The Earthmother and Glowing Guardian disapprove of Life Steal; attacking a monster will cause Glowing Guardian to immediately renounce you, while The Earthmother will both penalize you an (undetermined) amount of piety and set your Life Steal to 0%. Since there's no penalty for being renounced by Glowing Guardian, worshiping him for the one-time health boost may still be worthwhile if no better Gods are available.
While neither Mana Burn nor the reduction to Max Mana that accompanies Taurog's Boons affects the Vampire, it will be difficult to gain Piety with him if you're relying heavily on spellcasting. However, choosing Tuarog and converting all of your glyphs (both for Piety and for Life Steal) can be a viable choice, especially if a number of items which boost your combat effectiveness are available. With the right items and the Rage boon, a Vampire becomes nearly unstoppable.
While Mystera Annur provides boons which boost the effectiveness of BURNDAYRAZ, the fact that worshiping her effectively negates the Vampire's Life Steal makes her an extremely poor choice under most circumstances.
The Pactmaker is always a good option; you're likely to have explored as much of the map as possible from an early level, meaning a good chunk of starting Piety. With a little luck, it's entirely possible to purchase Learning before having killed a single foe.
Dracul is an interesting choice, although there are both pros and cons to be considered. On the one hand, it's risky for a Vampire to reduce his Max Health; doing so reduces the amount of Health returned by blood pools, and also limits your ability to chain BURNDAYRAZ. On the other hand, First Strike somewhat reduces the importance of a high HP total, while Bloodhunger stacks with a Vampire's natural Life Steal - making it possible to reach a whopping 50% Life Steal. When Dracul's bonuses to Attack Strength and Resistances are added in, the Vampire becomes incredibly difficult to kill - especially if items which further increase Damage or Resistance are available . As always, however, be careful of choosing Dracul on maps with lots of Undead.
A final option (testing needed?) is the Glowing Guardian + CYDSTEPP option. Glowing Guardian rewards piety for being saved by death and for using CYDSTEPP. If you have less health than it costs to use the glyph, it will immediately cast and save you from dying for a gain of 3 piety. You can do this as many times as you wish until you have 100 piety. At this point, you can easily transfer to The Earthmother or Binlor Ironshield and take their best boons (If they are available, and if you can avoid their retribution). Or simply stick with the Glowing Guardian's boons.
This is as straightforward as it gets. Explore as much as possible, to find BURNDAYRAZ and all level 1 Serpents and Nagas you can locate. Kill enough of them to go to level 2. Continue exploring if possible and repeat the process with the level 2 Serpents and Nagas. By level 3 you can probably start using BURNDAYRAZ to destroy high-level Enemies. Calculate the amount of damage you can dish out with the health you've got (heal it with blood-pools or potions if it can help take a higher-level one). This should lead to a chain of level-ups culminating around level 7. At 7, you can take out Medusa with a fireball volley. At 8 take out Jormungandr the same way - you should have plenty of potions left too, so this should be easy as pie.
Use the same method as above (see Snake Pit), except this time concentrate on Wraiths and Vampires at the start (after thoroughly exploring everything you can explore!). Go for Zombies only if you don't have any better target. You may want to set up a midfight level-up for your encounter with Frank the Zombie.
Yup, it's the same trick here. Your favoured targets should be the Warlocks and Imps, as they possess the least health. Since you'll be exploring the entire map anyway, Imps shouldn't be a bother at all. Go for Aequitas first.
Now this is the truly challenging part. In the factory, none of the enemies are as easy to take down as in other challenge dungeons. The Animated Armour requires a set number of hits to kill, the Meat Men have huge health, and the Golems are resistant to your BURNDAYRAZ. Patience here is the key, as is the help of the Pactmaker, so make sure you can locate him early (but don't join him yet!).
Begin by exploring as much of the dungeon as you can. Get as many good shop items as you can find (it helps being loaded with cash, so come prepared). Also find BURNDAYRAZ, you can't win without it. Once set, start taking out level 1 Golems. If you have good Lifesteal, you can take on Animated Armour and maybe even Meat Men - the regeneration will keep you safe, just make sure it says "SAFE" before attacking. Before leveling up to level 2, assuming you have explored thoroughly, join Pactmaker. This will net you a large amount of Piety from all the exploration.
At level 2, continue exploring if you can, and see if you can take out slightly higher-level targets. The moment you can't explore any further, level up again. At level 3 you can start taking on level 4 monsters, or level 5 Golems. Again the idea is to level up using as few monsters as you can find, but remember that lower-level monsters can be killed for Health (thanks to Lifesteal). The moment you have 80 Piety, immediately take Pactmaker's Health boon.
At level 7 make sure you have several monsters to level up with. Do not kill them before you start the boss fights! If you're low on health, try to replenish it by attacking lower-level Animated Armour: Your lifesteal should outweigh the damage they do to you, increasing your health instead of decreasing it for every attack. However do try to keep a few of them alive. Blast Super Meat Man with spells until you have about 50% of your health left. Then attack an Animated Armour to reduce your BURNDAYRAZ cost back to 6. Go at the meat man again. Then kill off a few of the monsters left to regain Health, but don't level up yet. Spend as much BURNDAYRAZ as you can still afford on the Super Meat Man, and then finally level up and finish him.
This will put you high up in level 8 or low in level 9. Repeat the process, making sure you are healthy and have enough low-level armors to attack (if any remain at all). Use the same tactic against Iron Man, attacking an Armour half-way through your health to reduce the cost of BURNDAYRAZ. Remember that this time you can use Potions and also drink up blood-stains on the map - this will be extremely helpful, as it can replenish your Health twice over if you've killed enough monsters. Also remember that when you are 10 points below leveling up, you can use Pactmaker's "Experience" boon to push you over the edge.