Gigantification

Eisen laid down in the bed covered by Kirisho's mist. For one, this would simply obscure Eisen further. Would allow him to get away by shrinking down instantly, without any intruder able to spot him. But it also had another benefit.

One of Kirisho's abilities was a sort of 'Domain', technically similar to what Eisen's Demonic Domain was, that she could establish. A domain where she was a lot more powerful for a certain period of time. This ability had an extremely long cooldown, so it wasn't viable to just use it whenever one wanted to. However, it seemed like this was a point at which she felt it was useful, for more than just one reason.

The fact that it produced a lot of mist with similar substance as the mist her body was made of, so that she could cover the whole bed. Also that it blocked any sound from coming in, and any sound from going out. The same was the case for visuals, of course. Nobody could see what was going on inside there.