The level 7 Dark Moon Disciple monk substitution level grants the monk—in exchange for the supernatural ability wholeness of body—the supernatural ability shadow blend that says
In any conditions other than full daylight, a 7th-level Dark Moon Disciple can disappear into the shadows, gaining total concealment. Artificial light does not negate this ability, though a daylight spell does. (Champions of Valor Web enhancement "Benefits of Membership" 6)
(Links mine.) This seems a pretty significant—perhaps even overpowered—buff. A creature with just total concealment can't be detected in the same ways that a creature that's merely invisible can be, for example. Neither the 2nd-level Sor/Wiz spell see invisibility (Player's Handbook 275) nor the 6th-level Sor/Wiz spell true seeing [div] (PH 296) obviate this total concealment, and it seems that a creature that possesses total concealment is immune to attacks of opportunity and targeted spells and that attackers that do manage to locate the square he's in will always suffer a 50% miss chance.
Although it's negated by full daylight and the spell of the same name, once the monk's taken a standard action to activate it, the shadow blend ability has no duration: a monk that stays out of the sun possesses total concealment forevermore. The only downside seems to be that once the ability is activated, it can't be deactivated except by strolling into a sunlit area! (Even this weakness of is likely an oversight.) That seems the sole downside… apart from the fact that to gain the ability shadow blend a creature must take seven levels of monk!
Please, answers, confirm or deny my understanding of this ability: Have I accurately assessed the power level of the supernatural ability shadow blend or am I overreacting? Similarly, is the ability as difficult to overcome as it seems? I know a monk usually needs all the help she can get, but is the ability shadow blend too much?
Note: Gnarg the orc ex-barbarian-turned-monk is approaching his seventh level of monk, and this DM doubts his ability to effectively challenge the PC once the PC gains this ability.