Solomon will have trouble controlling his magic in much the same way he did when he arrived, on a purely practical level. He'll also have shadows clustering around him at alternative intervals. Thanks to Asti's boon he still won't be feeling the addictive effects, though given the sharpness of clarity that offers he won't be having fun with that later on in the week, and will probably avoid places steeped in death/have trouble interacting with people with a lot of death around them.

Anton will start merging with the gist and feeling all those emotions the gist inhabits directly, which he hasn't properly done in, oh, five centuries. Since he won't know specifically what's happening he'll probably wind up clearing the Hotel and locking himself inside it, so he'll be hard to get to unless you have a key, know how to unlock the magic-locked doors or have enough raw power to get through the wards to break open a window or something.

(Dante, Raine and Skulduggery would all have keys.)

At the tail end of the week he's going to be very violent, very angry, and struggling very hard with keeping all that in check. And still be stupid powerful in the meantime.