The art is gorgeous, with an incredible sense of style and some lovely touches like the puppeteer dungeon master shadow, and the music is a perfect fit giving a strong michievous feeling :)
The central concept is excellent, and I really enjoyed trying out different combinations of creatures to test the strength of the adventurers. Loved the little snippets of dialogue - both in the intro and during gameplay when characters beat a stage or die - and I was delighted that it's a functioning chat feature so I could taunt them (also, your screenshot line in the images you've posted here really cracked me up - definitely a familiar feeling lol)
Would love to see this one expanded, with a little more information available about character/enemy hp or stats so I can adapt my strategy accordingly :)