Evocation [ Darkness ]
Level: Brd 2, Clr 2, Sor/Wiz 2
Innate Level: 2
Casting Time: 1 action
Duration: 1 round / level
Saving Throw: None
Spell Resistance: No
Metamagic: Extend, Quicken, Silent
Energy Substitution: Yes
A targeted area is shrouded in magic which darkens everything inside of it. Because it is magical, creatures who are inside or enter an area covered by Darkness are affected by the magic in different ways than one might expect a normal lack of light to act.
- If a creature has a specific spell immunity to Darkness, and does not have spell level absorption, it is neither darkened nor receives the special Darkness spell effects (i.e. it remains fully visible to creatures outside it).
- Else, if the creature created the Darkness, it gains the darkened appearance and Darkness-based invisibility
- Else, it gains the darkened appearance, Darkness-based invisibility, and Darkness-based blindness.
Darkness-based invisibility differs from spell-like invisibility in that the spell Ultravision is used instead of See Invisibility to negate its 50% concealment and negative modifiers to those trying to attack the affected character. The Darkness-based blindness effect differs from Blindness in that Ultravision and True Seeing is used instead of Remove Blindness to negate the lowered AC and inability to see at a distance on the affected character.
Regardless of the mechanical negation through vision spells, the visual blackness remains. This can make it difficult to physically target inside a field of Darkness. Players can use the <tab> key to highlight enemies so long as they can see through darkness, but this does not help to loot. A mage's immunity to their own Darkness-based blindness effect is less useful than it seems, because even if not blind, they cannot see others inside the field who have Darkness-based invisibility, without an appropriate vision spell.
While the casting of Darkness itself is not considered an "attack", the check to see if a creature is affected by the blindness-effect is. So a mage who casts Darkness and then Invisibility, may find their invisibility effect broken by someone else's, even other party members' or their own familiar's, entrance into an existing field. In the case of familiars, this "attack" can also serve to trigger the Henchman Bug.
Creatures outside the area are unaffected by the spell. This means, for instance, that an intervening area of Darkness will not prevent missile attacks from being used across it. They can also fire missiles at creatures inside the Darkness, subject to the normal mechanics associated with targeting invisible creatures, including significant benefits to those who have the Blind Fight feat.
The Darkness-based blindness effect has a well known Bioware bug called the Ultravision Bug. This can be fixed in Avlis through the use of the special Crafting Menu Option:  Special Functions ->  Fix Ultravision bug.