Bloodshadow has it right. The majority of fear and anxiety have roots in the unknown. People who are comfortable in the dark rarely fear it.
I personally associate darkness with the absence of light or energy. White objects, by their very nature, reflect all light towards a viewer, Black objects absorb it. I also think there are plenty of 'evil' things lurking about in the daytime. *lol*
If I was to suggest a card or effect that I think would fit with the whole vampirism/drain theme, it would a card/or creature ability that gives you the ability to switch a creatures power with their health. This would suggest a creature could feed off their own body to do more damage, or channel their power into hp for protection. It is like a rage potion in some regards though, so it may be a useless suggestion.
Alternatively, an effect to feed/leech off an enemy and switch your power/hp with a different target would also be cool. This would essentially be a one time use of the devour ability, that didn't kill off the target of the effect, and didn't transfer abilities. The transfer of abilities could perhaps come with an upgrade...
I haven't been through the majority of the forums yet, so please forgive if these have been said before.
