Focused Ranger (3.5e Alternate Class Feature)
From D&D Wiki
Rather than choose five types of creatures that you are an expert at hunting, you focus all of your abilities into one, increasingly specific, group.
Level: 1st and every five levels
Replaces: Favored enemy
Benefit: Hated Enemy (Ex): At 1st level, a ranger may select a type of creature or other defining characteristic from among those normal for a ranger, plus any group or guild, character class or other affiliation or defining trait, such as a template. The ranger gains a +2 bonus on Bluff, Listen, Sense Motive, Spot, and Survival checks when using these skills against creatures of this type. Likewise, he gets a +2 bonus on weapon damage rolls against such creatures.
At 5th level and every five levels thereafter (10th, 15th, and 20th level), the ranger selects a more specific enemy. The bonus against this more specific variant increases by 2. This new type of enemy must clearly be more specific than the previous, as determined by the DM. In addition, at each such interval, the bonus against any one hated enemy category (excluding the one just selected) increases by 2
At 10th level or higher, the ranger may instead pick a single, specific creature, and the bonus increases by 4 rather than 2. This creature can be picked again, but the bonus only increases by 2 each additional time. This creature need not fit into a previously chosen category, though it is suggested.
For example, At first level, a ranger picks aberrations. Then, at fifth, he picks mind flayers. Then, at tenth, mind flayer wizards. Then, at 15th, mind flayer wizards from the attack on his hometown, then finally Quaglath Mindrot, the wizard mind flayer commander of the group that razed his village to the ground.
If a specific creature meets some, but not all, of the rangers hated enemy requirements only the bonuses up to the one that does not apply stack. Taking the last example, if Quaglath was actually a sorcerer, the ranger would get bonuses either for the first two hated enemy bonuses, or the specific enemy he chose at twentieth level, whichever is higher.