Also, if anyone wishes to be a saint, the following bitmasks could use checking. Possibly they could be things like:
dt_undead (although this is more likely to be an unused effect #, see below), !sacred, oInanimates, !mcBeing, !demon, oAmphibious etc.
16384 - this is used by *lots* of spells. No idea what it does.
2, 4 - I'm guessing that these are dom1 or dom2 versions of commonly used flags (only undead?) which have been grandfathered in? Pure speculation on why these low values are never used.
256, 1024 - given what the nearby bitmasks do, I'm guessing these change damage types somehow. Are there any damage types that appear on weapons but never on spells?
134217728 - the adjacent bitmasks are oUndead, and some flag used to target spells into remote provinces (site searching, mind hunt etc.)
Also there are some conspicuously missing effect #s. I'm guessing that one of these is dt_antiundead, but other than that I have no idea:
5,6,9 - these are probably all damage types.
12 - reserved for a second set of affliction bitmasks? Just a guess.
14,16,18 - I'm guessing these are more out-dated effect codes replaced by new ones. I should really get a copy of dominions 1 and code-dive the corresponding table

.
And after that, half or more of the codes are missing, and I wouldn't bet that the missing codes do anything at all.