((Less stealth by Fleshbane means easier stealth for Ciel

))
Ciel takes full advantage of Fleshbane's entry to slip in undetected, unseen and unheard. Menek's taste in music is insufferable, but it was quickly cut off by one of his servants scolding Fleshbane. An added benefit of this approach.
The white void catches his eye, but before he explores that, Fleshbane has given him an opportunity to examine the manse. He will slip in following the breaking of the door and make a quick scope of the place, looking for anything he can use against Menek such as info on still-living relatives, acquaintances, journals containing personal information, all the way down to anything that might give him more information on how Menek's magical or investigative abilities work.
While doing this, he will keep an eye out for traps, both magical and nonmagical. He will try to avoid them, but for those that can't be avoided, he will attempt to disarm them without leaving traces of tampering.
While Fleshbane has made every effort to be detected, he is doing the opposite, going full-blown shadow on the wall, leaf in the wind. He will keep his search short so that he has time to examine the unformed area before Menek's return. He could have sworn he saw signs of life in there.
((Oh yeah, important question. Would Ciel have seen Mako and Menek leaving together, or would he and Fleshbane have arrived after they left? That will determine a bit of what Ciel looks for in the Manse.))