|Once you have unlocked all Gods, you may encounter the Crusader in a subdungeon. You must reach 100 with any deity in order to gain his trust, at which point you will unlock the class.|
While not apparent at first glance, the class features of the crusader allow him to be played in more ways than probably any other class. Learning to properly use all the gods, as well as getting comfortable with desecrating their altars at the right time allows you to unlock the full potential of the Crusader.
means you are resistant to most effects which hinder regen fighters, which makes you excellent at stacking damage resistances, even tough you don't start with any. It also makes you effectively immune to most of the maluses that Patches the Teddy can inflict upon the player, meaning you should probably be prepping it on any Crusader run (as it can also get you some resistances, but also all sorts of other benefits).
While resistance stacking is certainly strong, even a spellcaster crusader can benefit from the potential mana increases Patches offers. At very minimum, the ability to use Patches freely is very effective.
ability can be leveraged in two ways - by getting your attack very high (in combination with the highest base damage possible), to take down the boss in as few hits as possible. This is actually rather difficult to leverage, and while workable is probably the worst way to play crusader. It is occasionally the way to go - when you're facing a high damage but low health boss like Bleaty, Aequitas and such, or when you can only get a very, very few strikes in on a boss.
The best way to leverage it is to conserve popcorn (low level mosters) as much as possible during leveling. Then when you're ready to fight the boss you first kill 4 little guys for +60% damage, which is a lot and practically unparallel. You then strike the boss, and it drops to +30%. Kill two more little guys and you're back to 60% for the next strike. This is the most optimal way to play the crusader, and it makes him one of the highest damage classess in the game in a stable way.
means you will always have plenty of altars in the dungeon. This means you're more likely to encounter useful altars, and will have more opportunities for favorable conversion combos. This also means that it's somewhat more likely that you'll encounter the unpreppable god The Pactmaker. If combined with the extra altar preparation then a Crusader will have a total of 5 altars, meaning more than half the pantheon will be present. Perhaps most importantly, it vastly increases the odds of finding an altar you can safely desecrate for bonus piety.
Bringing a Burn Salve on any run means you can always desecrate The Earthmother altar with no effective downside. The Mystera Annur altar can be easily desecrated if you have a way of removing resistances from your enemies afterwards; both Binlor Ironshield and Jehora Jeheyu offer you a method of reversing her penalty. The Binlor altar can be desecrated for no punishment as long as you don't have any damage resistance, and since the Crusader doesn't have any by default this usually means it's a free desecration. Dracul's altar can be desecrated if you don't mind a minor health drop, but this can be problematic on high-difficulty dungeons where powerful monsters often come very close to 1-hit kills. The only altar which you should avoid desecrating at all costs is the altar of the Glowing Guardian.
A particularly effective combination is using Taurog and Dracul in combination for high resistances. Ordinarily any specific 2-diety combo requires some luck to find, but for the Crusader the odds are pretty good.
Which race is best for the crusader depends on which gods you intend to use. The trick to beaing a great crusader is choosing a race who's bonus helps you level up.
The Orc Crusader makes a great race for Crusaders. Due to his massive attack bonus, an Orc Crusader's heightened base attack will be multiplied to enormous proportions. An added benefit of playing an Orc is that early glyph conversions will help you level by killing higher level enemies saving a lot of "popcorn" for later to keep your damage boost from stable.
The Halfling makes a great race for Crusaders because of their many beneficial interactions with gods, the fact that you can use their healing potions in combination with in order to spike a boss and the fact that you can use your health potions to kill higher level monsters while you level. Potions can also be used to power up the Trisword and/or the Alchemist Scroll, and advanced users can make good use of converting potions for piety with the gods Glowing Guardian, Dracul or Jehora Jeheyu, and Tikki Tooki can turn health potions into freebie hits on the boss.
The Goblin (if you can use them) is also makes a rather good crusader, since he can use his conversion bonus to level up while killing fewer enemies, leaving more enemies on board to keep the end-game stable.
The Crusader can build up to massive amounts of attack bonus by chaining kills. This allows Crusaders to deal massive amounts of damage that other classes simply couldn't achieve with a single blow. On the other hand, this bonus is halved if he doesn't land a killing blow (including with BURNDAYRAZ, so watch out!), so he must repeatedly kill low-level monsters to rebuild his and deal his maximum damage. This makes it exceedingly important to leave lots of low-level monsters alive for the boss battle, and makes him work very well with deities like Tikki Tooki. Managing popcorn monsters is the most important part of playing Crusader, as you'll need them to kill higher level monsters or bosses faster.
One particularly devious strategy with the Crusader is the so-called "one-hit-wonder". This Crusader prepares a Strength Potion or purchases one in dungeon, and otherwise works to maximize his attack bonus (usually by playing orc and converting just about everything). He then builds up and activates the Strength Potion. This will grant him a single attack that deals massive damage. This is often enough to wipe out a weaker boss.