"Thank you for taking care of all the monsters, it made it so much easier getting to the treasure room. As promised, you can help yourself to as much as you can carry.
... Of course, that's going to be rather difficult after you become less than an inch tall. Oh, don't look surprised. You did read our contract, didn't you? Not to worry. Monster hunting may be far out of your league now but, I have a few pesky bugs you can deal with back at my shop.
No? Well, I might be able to find a fair price on the black market for some puny heroes. Or maybe you'd prefer serving as a little curio on some shelf. I'm sure I have a spare jar somewhere."

Xhang, one of my Pandaren, shrinks some heroes after using them to clear out all the creatures dwelling within an ancient Mogu tomb.