Sirens and Banshees are both Low Sky (it's sort of a joke about them riding brooms, kind of)
I... totally fucked up the Hawk Men, I forgot to have them promote correctly. I just now fixed it, here's a re-uploaded version.
http://dl.dropbox.com/u/8244840/OgreBattleNeph.smcAs for Giants, here are their updated stats:
Giants are unchanged, but you can find more of them earlier on.
Fire Giants get 4 Melee up front, 3 Fire Attacks in the back. 5 Strength per level, 1 int per level. 57 physical resist now, they also promote at level 8, 0-40 alignment.
Titans are magic-focused Giants, they get 3 melee up front and 2 int gales in the back. They get 3/3/5 (int) for stats. They promote at level 10, with 55-100 alignment.
There is that very small alignment area where you can't promote them but you can buy alignment pots from the first town, so... EDIT: No I didn't, I'm going to change that... hum dee dum.