From Compendium of Worldly Lore
The skittering of multiple legs across the floor, the droning of wings—these phenomena mark the passing of a vermin lord. This unthinkable entity prefers the caress of the crawling legs of an insect or the fluttering wings of a fly more than the touch of another person. The vermin lord offers itself as a host for all manner of parasitic organisms and insects that feed on it body. It not only allows the infestation, it revels in it.
Clerics and druids comprise the majority of the vermin lord ranks; some cleric/rogues are present as well. Many monstrous vermin lords, such as drider clerics, exist.
Humanoid vermin lords work with monsters such as driders, phase spiders, and other creatures associated with vermin. Otherwise, they operate alone, for most other humanoids will have nothing to do with them.
Role: Spell Utility
Characteristics: Casters devoting themselves to vile crawling creatures in exchange for horrifying abilities and command of said creatures
Source: Book of Vile Darkness
Game Rule Information
The Vermin Lord has the following game statistics.
Abilities: Charisma for befriending vermin, casting stat if charisma isn't it already, standard caster battery of dexterity and constitution for staying alive.
Alignment: Any Evil
Hit Die: d6
Starting Gold: N/A
Class Skills
The Vermin Lord's class skills are Bluff (Cha), Climb (Str), Concentration (Con), Hide (Dex), Knowledge (nature) (Int), Listen (Wis), Move Silently (Dex), Perform (Cha), Pick Pocket (Dex), Search (Int), Spellcraft (Int), and Spot (Wis).
Skill Points at 1st Level: (4 + Int modifier) × 4
Skill Points at Each Additional Level: 4 + Int modifier
Class Features
All of the following are class features of the Vermin Lord.
Weapon and Armor Proficiency: A Vermin Lord is proficient with whatever they were already proficient with prior to taking levels in this class.
Spells: When a vermin lord gains 1st level, and every two levels after that (plus 10th level), the character gains new spells per day as if she had also gained a level in whatever spellcasting class she belonged to before she added the prestige class. She does not, however, gain any other benefit a character of that class would have gained (improved chance of controlling or rebuking undead, metamagic or item creation feats, hit points, beyond those received from the prestige class, and so on), except for an increased effective level of spellcasting. This essentially means that she adds the new level of vermin lord to the level of whatever other spellcasting class the character has, then determines spells per day, spells knowns, and caster level accordingly. For example, if Silican, an 8th-level wizard, gains a level in vermin lord, he gains new spells as if she had risen to 9th level in wizard, bus he uses the other vermin lord aspects of level progression such as base attack bonus and save bonus. If he next gains a level of wizard, making him a 9th-level wizard/ 1st-level vermin lord, he gains spells as if she had risen to 10-th level wizard.
If a character had more than one spellcasting class bebore she became a vermin lord, she must decide to which class she adds the level of vermin lord.
Chitin Ex: A vermin lord gains a +1 natural armor bonus to Armor Class from the chitinous plates that begin to grow on his flesh. Every three levels beyond the 1st, this bonus increases by +1.
Vermin Servant: A vermin lord gains a servant in the for of a vermin of up to 1 HD. This servant is treated as a familar, its intellegence increases, and its considered a magical beast (see the Familiars section in chapter 3 of the Player's Handbook). The vermin servant is in addition to any familiar the character may already have.
A vermin lord gains additional servants at higher levels. at 5th level, the vermin servant gained can be up to 4 HD. At 9th level, the vermin servant may be up to 16 HD,
Blood Drain Su: A 2nd-level vermin lord can grow insectoid mandibles at will. He can use these mandibles to make a bite attack that deals 1 point of damage. Furthermore, the vermin lord can attempt to start a grapple, provoking no attack of opportunity. If successful, the mandibles automatically deal 2d6 points of damage each round as they suck blood from the victim. The blood drain ability only works on living creatures.
Spider Hand Sp: Once per day, a 3rd-level vermin lord can produce an effect identical to that of a spider hand spell cast at his effective caster level.
Swarm Armor Su: Each day, 4th-level vermin lord automatically summons a swarm of insects, spiders, or scorpions that cover his flesh when he regains his spells. these insects absorb up to 10 points of damage from and damaging attack (weapons or spells). the insects die off when they absorb such attacks, and a total of up to 5 points per vermin lord level can be absorbed per day. Thus, a 7th-level vermin lord's swarm armor can absorb up to 35 points of damage, although no more that 10 points from any one attack.
If a vermin lord is already wearing armor, the swarm armor has no effect.
Wings of the Vermin Su: A vermin lord of 5th level or higher can sprout massive, buzzing insectoid wings from his back once per day. With these wings, he can fly at his normal land speed with average maneuverability for 1 hour. The vermin lord can carry his normal carrying capacity, and greater burdens affect his speed as they would affect his land speed. It is impossible to move silently with these wings.
Spider Legs Sp: Once per day, a 6th-level vermin lord can produce an effect identical to that of a spider legs spell cast at his effective caster level.
Spew Vermin Sp: Once per day, a 7th-level vermin lord is able to spray out a swarm of vermin from his mouth, as a breath weapon in a 30-foot cone. Anyone in this area takes 1d6 points of damage per vermin lord level, with a successful Reflex save reducing the damage by half (DC 10 + vermin lord's class level + vermin lord's Con bonus). These vermin then remain as if a summon swarm spell had been cast at the vermin lord's class level. The vermin are under the command of the vermin lord.
Poison Ex: In a vermin lord of 8th level or higher, the mandibles gained from the blood drain ability now carry a natural venom that deals 1 point of Strength damage with each successful bite attack, and 1 point of Strength damage 1 minute later. The Fortitude save DC to resist the poison is 10 + vermin lord's class level + vermin lord's Con modifier.
Hivemind Su: A 10th-level vermin lord can form the impetus to create a hivemind (see Hivemind in chapter 2). The hivemind must include the vermin lord, although he counts as only a single individual and his intelligence and Charisma scores are unaffected. However, he controls the hivemind, gains insight bonuses, and can take advantage of the spellcasting abilities of the hivemind if enough individuals are present. The vermin lord's vermin servant can also join the hivemind if the vermin lord wishes.