How does Reputation work in Heroes VI? (Blood and Tears)

It is an either/or choice, as reputation controls the class of your hero. Once you have enough Blood points or Tears points, your hero changes class and gains a new ability. You then get the chance to fill the points bar a second time (but only with the same type of points), which gives you an advanced ability for your class.

As in previous Heroes games, each faction has a might based hero and a magic based hero. In Heroes VI, each faction also has a might or magic based Blood hero and a might or magic based Tears hero, for a total of six classes per faction.

Shamelessly stolen from the Heroes VI website, the following table lists all the hero classes available:

Haven

Name           Type      Reputation
Knight         Might     Neutral
Cleric         Magic     Neutral

Paladin        Might     Tears
Confessor      Magic     Tears

Vindicator     Might     Blood
Inquisitor     Magic     Blood

Inferno

Name           Type      Reputation
Heretic        Might     Neutral
Warlock        Magic     Neutral

Hellcaller     Might     Tears
Demonist       Magic     Tears

Chaos Lord     Might     Blood
Pyromancer     Magic     Blood

Necropolis

Name           Type      Reputation
Ebon Knight    Might     Neutral
Necromancer    Magic     Neutral

Bone Guard     Might     Tears
Embalmer       Magic     Tears

Death Knight   Might     Blood
Reaper         Magic     Blood

Stronghold

Name           Type      Reputation
Barbarian      Might     Neutral
Shaman         Magic     Neutral

Chieftan       Might     Tears
Earth Shaper   Magic     Tears

Warmonger      Might     Blood
Storm Caller   Magic     Blood

Sanctuary

Name           Type      Reputation
Samurai        Might     Neutral
Monk           Magic     Neutral

Shogun         Might     Tears
Tide Master    Magic     Tears

Warmaster      Might     Blood
Flood Conjurer Magic     Blood

Your goal with earning alignment is to get to one side or the other. Earning points from one side DOES NOT cause you to lose points from the other side, so you can feel free to build up both at the start.

Earning a reputation level not only allows you access to an additional skill, but it also strengthens skills that are associated with that reputation. For example, Ice Bolt is a Blood spell, and it does additional damage if you are at Blood Level 1 (250 reputation) and even more at Blood Level 2.

The skills you take during a normal level up mostly affect this in terms of what points you are earning. There are a number of skills that award blood or tears points each time you use them, so you should generally select skills that work with the path you are heading for.

Keep in mind though that this is just one way to earn blood and tears points, and in my limited experience so far, it is actually a pretty minor one. You also earn points when a neutral army tries to run away from you (10 blood by chasing them, 10 tears by letting them go) and at certain points in each scenario where you can make a choice that I've seen award 50-100 points.

Tears and blood are the two sides of the alignment system in Might and Magic Heroes 6. You can only have points on one side, if you gain point of the opposite side, you'll first lose the one you already have until you reach zero.

Your alignment is affected by several factors, like the actions you takes (pursuing fleeing monsters, e.g.) and the spells you uses. Gaining enough points on one side will grant you bonus abilities that you can see over the alignment bar on the character screen.