Rather than any particular group of set of beliefs, Zhentarim is the word used to denote a mindset of warrior. A combatant that focuses on the use of intimidation, and values the use of fear as just an effective tool of war as physical force is. Although there is a preconceived notion that Zhentarim are 'evil,' and it is likely that they would be found to be callous or mercenary, there is no hard and fast rule about who can become a Zhentarim even though many 'evil' warlords may use fear to inspire loyalty. Intimidation is just another weapon to a Zhentarim, it's how you use it that counts.
Famous Zhentarim often gain great notoriety in the realms for their use of fear tactics, but as with most things it tends to be the bad apples that gain the attention of the masses. Warlords and criminals mix intimidation with torture and other nefarious means to get their way, and so the general view of using fear tactics is less than friendly. Of course, it's just a tool, and being one tactic amongst many means that although some may throw around the word 'Zhentarim' it doesn't really mean anything beyond a description of its base parts.
Few truly follow the path of breaking men for whatever purpose it is that draws them to the call, but those that do would be unlikely to refer to themselves with the label. It is a title that is earnt and given, not one which a person claims. Just as a person cannot claim to be a champion, so must the mantle of 'breaker of men' be forged out of sweat and blood.
Requirements: To take a Zhentarim substitution level, a character must be about to take his 3rd, 5th, or 9th level of fighter. The features listed below replace any features that the fighter might normally have gained at the levels that the substitution is taken for.
Class Skills: A Zhentarim fighter has the same selection of class skills as a standard fighter does, plus Bluff and Diplomacy.
Skill Points at Each Level: 2 + Int modifier. Level BAB Fort Ref Will Special 3rd +3 +3 +1 +1 Bonus feat 5th +5 +4 +1 +1 Extended intimidation 9th +9 +6 +3 +3 Swift demoralization
Bonus Feat : A Zhentarim gains Skill Focus (Intimidation) as a bonus feat at 3rd level.
Extended Intimidation (Ex): A target successfully intimidated by a 5th-level Zhentarim Soldier suffers lasting effects. Instead of ending when the Zhentarim leaves, as is normal for the Intimidate skill, the intimidation effect lasts for 24 hours after his departure. Thereafter, the target’s attitude toward the Zhentarim shifts to unfriendly, but a lingering fear remains. Whenever the Zhentarim returns to someone he has previously intimidated, he gains a +4 bonus on his Intimidate check to re-establish the effect.
Swift Demoralization (Ex): A 9th-level Zhentarim can use the demoralize opponent aspect of the Intimidate skill as a swift action rather than as a standard action.