What classes grant Mettle?

[Krafen]

In what book does Fist of Raziel appear?

 

[Mistwell]

In what book does Fist of Raziel appear?

Book of Exalted Deeds. It's a class intended for Paladin or Cleric-type casters. Full base attack bonus plus full caster progression except for the first level. Grants various advancements and bonuses to your smiting ability. Also constant circle of protection from evil, which also adds +2 resistance bonus to saves vs. spells from evil opponants. I don't think it's a "broken" prestige class (particular when combined with favored soul instead of cleric), but I do think it's a pretty good one.