O texto é conciso, mas não é ambíguo.
Shadowy Mist Form (Sp): At 10th level, a stygian slayer can transform into an inky black cloud of mist. This functions as gaseous form, except it also obscures vision as fog cloud. The slayer can use this ability for a number of minutes per day equal to his level. These minutes need not be consecutive, but must be used in 1-minute increments. This ability replaces the advanced slayer talent gained at 10th level.
Isso significa que isso é feito
The subject and all its gear become insubstantial, misty, and translucent. Its material armor (including natural armor) becomes worthless, though its size, Dexterity, deflection bonuses, and armor bonuses from force effects still apply. The subject gains DR 10/magic and becomes immune to poison, sneak attacks, and critical hits. It can't attack or cast spells with verbal, somatic, material, or focus components while in gaseous form. This does not rule out the use of certain spells that the subject may have prepared using the feats Silent Spell, Still Spell, and Eschew Materials. The subject also loses supernatural abilities while in gaseous form. If it has a touch spell ready to use, that spell is discharged harmlessly when the gaseous form spell takes effect.
A gaseous creature can't run, but it can fly at a speed of 10 feet and automatically succeeds on all Fly skill checks. It can pass through small holes or narrow openings, even mere cracks, with all it was wearing or holding in its hands, as long as the spell persists. The creature is subject to the effects of wind, and it can't enter water or other liquid. It also can't manipulate objects or activate items, even those carried along with its gaseous form. Continuously active items remain active, though in some cases their effects may be moot.
exceto que obscurece a visão assim:
A bank of fog billows out from the point you designate. The fog obscures all sight, including darkvision, beyond 5 feet. A creature within 5 feet has concealment (attacks have a 20% miss chance). Creatures farther away have total concealment (50% miss chance, and the attacker can't use sight to locate the target).
A moderate wind (11+ mph) disperses the fog in 4 rounds; a strong wind (21+ mph) disperses the fog in 1 round.
The spell does not function underwater.
Colocando as partes corretas de todas as três juntas, conforme indicado pelo texto, obtemos a descrição da habilidade:
Shadowy Mist Form(Sp): At 10th level, a stygian slayer can transform itself and all its gear become an inky, insubstantial, black cloud of mist. Its material armor (including natural armor) becomes worthless, though its size, Dexterity, deflection bonuses, and armor bonuses from force effects still apply. The subject gains DR 10/magic and becomes immune to poison, sneak attacks, and critical hits. It can't attack or cast spells with verbal, somatic, material, or focus components while in gaseous form. This does not rule out the use of certain spells that the subject may have prepared using the feats Silent Spell, Still Spell, and Eschew Materials. The subject also loses supernatural abilities while in gaseous form. If it has a touch spell ready to use, that spell is discharged harmlessly when the gaseous form spell takes effect. The mist obscures all sight, including darkvision, beyond 5 feet. A creature within 5 feet has concealment (attacks have a 20% miss chance). Creatures farther away have total concealment (50% miss chance, and the attacker can't use sight to locate the target).
A gaseous creature can't run, but it can fly at a speed of 10 feet and automatically succeeds on all Fly skill checks. It can pass through small holes or narrow openings, even mere cracks, with all it was wearing or holding in its hands, as long as the spell persists. The creature is subject to the effects of wind, and it can't enter water or other liquid. It also can't manipulate objects or activate items, even those carried along with its gaseous form. Continuously active items remain active, though in some cases their effects may be moot.
The slayer can use this ability for a number of minutes per day equal to his level. These minutes need not be consecutive, but must be used in 1-minute increments. This ability replaces the advanced slayer talent gained at 10th level.
Entre outras coisas, isso deve esclarecer que a forma de névoa do assassino sytgiano não é do tamanho de uma área de efeito da magia Nuvem de neblina .