[Nick_K]

Demons and the like are powerful enough as is. If they're given the ability to attack without being subject to enemy blows then there might be some very serious problems with all-flyer armies becoming the only viable tactic. In dominions even ethereal units are subject to normal attacks.

Flyer already gives the ability to cross all terains and attack behind enemy lines, the ability to instantly jump to anywhere on the battlefield and to instantly escape without being run down in a rout. It's a powerful ability.

There are many more significant areas that require suspension of disbelief than this. Including ones core to the genre such as the idea of explosive growth from a single province.