Other possibilities could be (carefully!) using the Mob template from DMGII on a bunch of regular skum, or putting a high-level aboleth (or some allied race) cleric in there who specialises in buffing spells. A skum is just a skum, but a skum under the influence of mass bulls strength, mass cat's grace, haste, prayer, bless, and hero's feast is quite a bit nastier. Add a creepy tentacled bard of some description (with the Song of the Heart feat from Eberron, and the Inspirational Boost spell from Complete Adventurer) and you can stack a +4 or more to attack and damage on top of that. Sprinkle liberally with poisoned weapons and tanglefoot bags, and you're golden...