She has to go insubstantial again. 

Doing it for the length of a heartbeat isn't too bad.

Okay. How far apart are those glass things, she wants to swipe two at once and make a run for it.

None of them are closer together than a meter but there's a couple of small ones just a little farther apart than that nearish the portcullis. 

Yoink and RUUUUUUUN

And when she reaches the circle around the alabaster platform, the sleepy boss monster is actually visible from the base, because she is significantly more vertical and substantially less sleepy. 

Not none, though. 

She yawns and rubs her eye with the heel of one palm as she looks around. 

Boss monsters are NOT allowed to perceive May or things on her person.

She frowns and looks around and does not spot May and heads in towards the castle, tiny dragon winging circles around her head. 

Exit still works, right?

Right. 

Out she pops with her swag.

The swag does not vanish. It continues being a sort of rounded blue chip and magenta-ish not-quite-a-hershey's-kiss shape made out of a material not totally unlike glass. 

It was not expected to vanish! It is expected to be sold to industrial R&D departments so they can reverse engineer it.

Cricket's waiting for her outside the dungeon. She calls her agent to talk about auctioning the loot. And also just to talk. She sends June an emoji.

If she's monitoring the situation with the portal at all, she may find out that Sleepy Boss Monster walks out of it and then it vanishes. 

Yeah she notices that! That's bad! That gets called in to her agent and also the provincial government!

Sleepy Boss Monster looks around, spots a winged cat, and walks over. 

"Hello." 

Shit shit shit. May texts more frantically. Forces herself to loosen her hold on Cricket so he can fly away on his own two wings if he needs to.

"You've got a lot of nerve," says Cricket, because he can't be polite to save his life.

Blinkblink. 

"...What, tal...king? To you? If I'm supposed to make an appointment first then..." she pointedly looks around at the lack of (visible) other people in the vicinity. "There would rather have to be someone to make an appointment with."

"Well, actually you probably aren't worth my talking to at all whether you found my secretary or not, but mostly the dungeon." Paw-lick.

"...My castle doesn't have a dungeon."

"The whole dimension beyond the portal, that's the dungeon."

"...Is this some meaning of the word 'dungeon' that I'm not familiar with? Because dungeons are for imprisoning people, and my pocket dimension isn't."

"It sounds like there is, yes."

"Well, I don't know what there is that could be objectionable about a 'dungeon' if it doesn't involve imprisoning people! --Although, actually--I don't suppose you know of anyone who went in--or if you went in yourself--I promise I'm not mad but something was--well--I guess it's arguable between 'stolen' and 'kidnapped' but, like, going with the latter would be sort of difficult to explain so I'm going to go with 'stolen.' I'm not going to be mean about it but I really need them back."

"What're you going to do about that?"