In D&D 3.0, the darkness spell was a sphere of blackness, impenetrable even to darkvision, which was terrifyingly powerful (except against demons and devils).
In D&D 3.5, it's a zone of 20% concealment, even to creatures with darkvision, which is annoying and frustrating for PCs of races with darkvision.
In Pathfinder and Trailblazer, it's a reduction in light level… which usually generates concealment but doesn't apply to creatures with darkvision, which makes it pretty weak given how common darkvision and low-light vision are.
How did the spell operate in earlier editions of D&D? Did it affect creatures with dark- (er, infra-) vision? If it did, is it known why it was designed in this way?
Best Answer
Here is the AD&D first edition version.
First, it depends on whether you are talking about the clerical or mage version. The clerical Darkness was actually the reverse of the Light spell. The PH makes no mention of how it affects infravision or ultravision... only the duration and area of effect.
Now the Mage spell, Darkness 15' radius, does state that "total, impenetrable darkness in the area of effect. Infravision and Ultravision are useless. Neither normal nor magical light will work unless a light or continual light spell is cast. In the former event, the darkness spell is negated"
Why was the spell nerfed? To provide more challenge to the players one must assume.
Now here's the original reference to Darkness. There was no Darkness spell in (basic) D&D. It was added in the Expert D&D expansion, and was referenced as a reversal of the Light spell. It was considered the same for both cleric and mage. It was described as a circle of darkness 30' in diameter that would block all light, but would allow infravision to work. A light spell cast on it would cancel it, and a failed save after casting it on someone's eyes would blind them.