Kodam said:
The Vampires ability works like the spell, doesn't it? The spell description says: "The subject also loses supernatural abilities while in gaseous form."
Not necessarily.
SRD said:
Gaseous Form (Su): As a standard action, a vampire can assume gaseous form at will as the spell (caster level 5th), but it can remain gaseous indefinitely and has a fly speed of 20 feet with perfect maneuverability.
1. It's a supernatural, not spell-like, ability, and so need not follow the rules of the spell.
2. If the vampire actually lost his Su abilities when assuming gaseous form, he'd lose the ability to assume gaseous form, and then where would we be?
However, I understand the argument that you're making.
The question, therefore, is:
When a vampire assumes gaseous form, he loses access to [most] supernatural abilities. What does this mean for an ability with an ongoing duration after use, should he change into gaseous form after he uses that ability?
More generally speaking, is the vampire's Su ability the ability to enspell people with his gaze, or is it the ability to enspell people with his gaze and then control them at a future point in time?
The nearest analogy I can think of is a wizard (or sorceror) who casts Dominate Person on an opponent and then suffers level loss sufficient that they can no longer cast that spell. Do they retain the ability to issue commands through the link?
Therefore, while I agree that the vampire cannot issue any new commands through the link in the situation above, the effect is still on-going, and the vampire can begin issuing commands again as soon as he reforms. Succinctly, the Su ability is the ability to enspell people with his gaze, and he loses this while in gaseous form.
Similarly:
SRD said:
Children of the Night (Su): Vampires command the lesser creatures of the world and once per day can call forth 1d6+1 rat swarms, 1d4+1 bat swarms, or a pack of 3d6 wolves as a standard action. (If the base creature is not terrestrial, this power might summon other creatures of similar power.) These creatures arrive in 2d6 rounds and serve the vampire for up to 1 hour.
A vampire in gaseous form cannot call forth the animals above. However, if he shifts to gaseous form *after* calling them, the animals are not suddenly freed of their compulsion to serve him.