Raxivort
The Rat Lord, The Burning Hand

Lesser God, Xvart pantheon
God of Xvarts, Rats, and Bats

Symbol Blue flaming hand  
Alignment Chaotic Evil  
Shaman Alignment CE, NE, CN  
Plane Pandemonium  
Worshippers Xvarts, wererats, some werebats  
Race Xvart or lycanthrope  
Sex Any  
Attributes Dexterity 13 -1
Proficiency Groups Rogue, Priest, General 5
Bonus Proficiency Throwing 2
Preferred Weapons Throwing dagger, throwing knife  
Allowed Weapons Small blades, hand axe, spear, javelin, sling, flail, club, morning star 5
Armor Chain mail or lighter armors, any shield -5
Primary Sphere Animal 10
Major Spheres All, Chaos, Combat, Elemental (Fire, Earth), Wards 45
Minor Spheres Guardian, Healing, Plants, Travellers 16
Additional Spells Burning Hands (as 1st level Wizards spell), Find Traps (2nd level), Neutralize Poison (4th level) 2
Abilities
  Xvart followers 5
  Spirit powers: ancestor and animal 30
3rd level +1 to hit with daggers and knives
4 (as expertise) - 1 (3rd level) = 3
3
5th level A mobat companion (+2 hp/die, similar to paladin's warhorse but not rideable) will join the shaman
10 (base) = 10
10
7th level +2 to hit with daggers and knives, one extra throw per round
8 (as specialization) - 1 (7th level)
7
  Shapechange up to 3 times per day into normal or giant bats and rats
15 (as druid ability) = 15
15
9th level Summon 2d6 4 HD mobats (1/day, in appropriate areas only)
5 (1/day) + 5 (P5, Animal Summoning II) - 4 (level 4) = 6
6
Limitations
  Hit points (d6) and THACO as Thief -20
  Obvious casting: blue fire surrounds the caster's dominant hand during spell casting. All spells require a Somatic component if they didn't already. -5
  Talisman: the shaman's holy symbol must be bound to Raxivort in a special ritual, and cannot be easily replaced -8
  Taboo: the shaman must avoid all contact with water or ice -- getting wet results in the loss of all shaman abilities until the shaman dries off -2
Raiment Blue armor or clothing, silken overgarments when available  
Animals Rat, bat  
Holy Days New moons of Luna (3 day celebration and rituals), sacrifice of captured treasure  
Notes
The Animal sphere spells are usable only on non-magical subterranean, burrowing or nocturnal creatures, including appropriate reptiles and invertebrates. Spells that are usable on a wide group of creatures may be cast on any valid target -- for example, charm person or mammal may charm a fire beetle, but snake charm still only functions on snakes.
The Plant sphere spells are only usable on subterranean plants and all types of non-intelligent fungi
Nearly all of Raxivort's shamans are xvarts, although has a few lycanthrope worshippers (most wererats worship Incabulos)
Raxivort's shamans do not typically rule their tribes, though they are respected advisors. They tend to be rather pungent, due to their aversion to water -- they maintain this marks them as holy. Some of his shamans are also mages of small skill.
Background
Raxivort was a servant of Graz'zt, chief amongst all xvarts. He rose to become Master of Slaves for the dark lord, and grew arrogant in his power. He rose up against Graz'zt, confidant he could usurp his power, and the two warred for months, xvarts and slaves against Graz'zts demonic legions. Raxivort was eventually forced to sue for peace and withdraw to Pandemonium -- but he captured a portion of his lord's true power (as well as much of Graz'zt's treasury), and with time has grown into a formidable power himself.

The shamans of Raxivort seek wealth and comfort for their tribes, and prefer to inhabit captured housing whenever possible. They are capable in a fight (for xvarts), but prefer to leave the battles to "more expendable" warriors, and to summoned animals. Cunning and survival are their watchwords, although the safety of their tribe comes before their own.

Sources
A Guide to the World of Greyhawk, p. 75 (original source)
Glossography of the World of Greyhawk, p. 46