Re: Neogi and Umber Hulks - air breathing?

In cases like this, DMs are more or less left to their own devices. In  
3.0/3.5 Neogi are aberrations which is applies to those critters that are of  alien 
mind set, of alien form, of alien physiology or any combination of the  
three. Alien as a term in this case refers to conditions not conforming to what  is 
generally know about the nature of things; not necessarily from outer space.  
Although depending on the campaign many aberrations could originate from 
worlds  outside the campaign world as opposed to alien dimensions orplanes of 
existance  like the Far Realm which many aberrations in the main stream now are 
supposedly  from.