At 2nd level, once per round a mountebank can decide to attempt to hide her spell’s manifestations from others, making it appear as though she is doing nothing at all. The attempt to hide the spell slows her casting slightly, such that spells that normally take a swift action now take a move action, spells that take a move action now take a standard action, and spells that take a standard action now take a full-round action, and spells that normally take longer than a standard action take twice as long (free action spells still take a free action).
To discover the mountebank’s ruse, a creature must succeed at a Perception or Spellcraft check (the creature receives an automatic check with whichever of those skills has the highest bonus) against a DC equal to 15 + the mountebank’s number of ranks in Stealth + her casting ability modifier. If the mountebank has a drawback which has an obvious visual or auditory display such as somatic casting or verbal casting, this DC is reduced by 5 for each such drawback, to a minimum of DC 0 (this ability does not hide the visual or auditory display, but rather causes those who see the mountebank casting and fail this check to not notice the display is due to spellcasting). If the mountebank has the virtuoso boon, the DC increases by 5 (the skilled caster drawback does not add to the DC in this circumstance).
If an opponent fails its check, the mountebank’s casting also does not provoke attacks of opportunity, and an opponent that fails its check can’t use readied actions that depend on realizing that the mountebank is casting a spell, or readied actions such as counterspelling that require identifying the spell the mountebank is casting. Spells such as those from the Destruction sphere that create an additional obvious effect (aside from the manifestation of casting that all spells share) still create that effect, though it might not be obvious who cast the spell unless it emanates from the mountebank.
If a character interacts with the mountebank long enough to attempt a Sense Motive check without realizing she have been casting spells, that character can use Sense Motive to gain a hunch that she’s behaving unusually.
At 7th level, the mountebank no longer increases the casting time needed while using her veiled magic class feature.