It seems that vanilla 3.5 doesn't really have DCs for poisons, so TW just asks DMs to wing it. Based on prices of the requested poisons compared to some in TW, I'm going to rule...<br/>Black adder venom has a DC of 15.<br/>Drow poison should be renamed, obviously, and has a DC of 15.<br/>Carrion crawler brain juice can keep it's name if you really want to tempt fate and has a DC of 20.