I think i can explain Mind Puppeteer concept.
For example, i play Mind Puppeteer and choose Petrified Minotaur from your hand. originally, its effect is:
-5 enemy wall
attack 5
wall +5
You pay price of that card, as if you played it. But first two effects will be applied to you, not to me. Third effect will be unreversed, because it affects player, who plays it, and will apply to you also. So, in summary effect will be:
-7 your bricks
-5 your recruits
-5 your wall
5 damage to you
+5 your wall