I find myself stopped up short in my efforts to create a major...well, not antagonist, but let us call him a very shady ally, for my PCs. The individual in question, Mykael the Grinner, is the master of a tribe of elves that favor incredibly toxic poisons, venoms, and chemical compounds. The trouble is that all the rules I can find for these substances (and spells that mimic them!) in 3.5 is highly underwhelming. Thus, I have two questions: are there any published resources that can help improve his lethal concoctions, and if not/in addition to those, does anyone have homebrew resources that they might suggest for such venoms?
To add some homebrew poison support, here are a few:
And to toot my own horn: I have performed an overhaul of the 3.5 poison system myself. It's not so much an addition to as it is a replacement of the old mechanics, but it does make them significantly more usable, and less reliant on being expanded in the first place (but I would think that, of course).
The best resource available for 3.5 poisons is the Arsenic and Old Lace handbook.
Anyway, Master of Poisons from Drow of the Underdark is a must. For one feat, get poison use and the ability to apply poisons as a swift action. Levels in shaper to manifest psionic minor creation is also a tried-and-true way to get poisons en masse very cheaply. Wild Cohort for a viper of some sort is also good for cheap poisons.
The variant bard found in Athas.org’s Dark Sun Campaign Setting (a WotC-licensed but not WotC-published work) has some nifty poison-related features. They’re not amazing, though.
Book of Vile Darkness is your best friend here, for it features poisons with really high DC. Unfortunately, the most potent ones are injury poisons.
The only caveat is the cost of the top poisons; it can be circumvented by liberal application of minor creation or by crafting cost mitigation.